Tập hợp nào sau đây có đúng một tập hợp con?
Hãy suy nghĩ và trả lời câu hỏi trước khi xem đáp án
- Tập {0; x} có 4 tập con: $\varnothing$, {0}, {x}, {0; x}
- Tập {x} có 2 tập con: $\varnothing$, {x}
- Tập {0} có 2 tập con: $\varnothing$, {0}
- Tập $\varnothing$ có 1 tập con: $\varnothing$
Câu hỏi liên quan
Kĩ năng nào sau đây được xem là phức tạp hơn cả trong số các kĩ năng đã cho?
Thường trực Hội đồng nhân dân có cơ cấu tổ chức bao gồm những ai?
Việc con người sử dụng các sản phẩm hàng hoá, dịch vụ để thoả mãn nhu cầu sản xuất và sinh hoạt là đang thực hiện hoạt động kinh tế nào?
Để xác định niên đại xây dựng vòng tròn đá Stonehenge ở Anh, các nhà khoa học đã sử dụng phương pháp carbon phóng xạ. Họ khai quật di tích hữu cơ nằm ngay dưới những tảng đá này để phân tích. Kết quả cho thấy tỉ lệ số hạt \(^{14}C\) và \(^{12}C\) trong mẫu chất bằng 56% tỉ lệ được tìm thấy trong các sinh vật sống. Biết rằng đồng vị phóng xạ \(^{14}C\) có chu kì bán rã khoảng 5730 năm. Từ kết quả đo đạc đó, em hãy xác định vòng tròn đá Stonehenge đã được xây dựng cách đây bao nhiêu thế kỉ? Lấy kết quả xấp xỉ đến hai chữ số thập phân.
Giá trị nghệ thuật của đoạn trích là gì?
Rô to của máy phát điện ở Hòa Bình quay 125 vòng trong 1 phút. Tốc độ góc của Rô to này là
Read the following passage about Traveling and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questions from 23 to 30.
Traveling and exploring new places is an exciting way to experience different cultures and expand one’s horizons. Whether it’s a short trip to a neighbouring town or a long journey to a foreign country, stepping out into the world offers numerous benefits. It allows individuals to gain new perspectives, meet diverse people, and create lasting memories. Additionally, traveling can enhance personal growth and provide a sense of adventure and fulfillment.
One of the key advantages of traveling is the opportunity to learn about different cultures. By immersing oneself in a new environment, travellers can gain a deeper understanding of local customs, traditions, and lifestyles. This cultural exchange fosters mutual respect and appreciation among people from different backgrounds. Moreover, experiencing different cultures can challenge preconceptions and broaden one’s worldview.
Traveling also promotes personal development. Facing unfamiliar situations and overcoming challenges can boost confidence and adaptability. Travelers often find themselves navigating new cities, trying unfamiliar foods, and communicating in foreign languages. These experiences can enhance problem-solving skills and resilience. Furthermore, the sense of accomplishment from successfully managing a trip can lead to increased self-esteem and a greater sense of independence.
Another benefit of traveling is the chance to disconnect from the routine of everyday life. Exploring new places provides a break from the usual responsibilities and stresses. This can be refreshing and rejuvenating, allowing individuals to return home with a renewed sense of energy and perspective. Travel can also foster creativity by exposing individuals to new sights, sounds, and ideas.
Despite its benefits, traveling can also present challenges. Planning a trip requires time and effort, and unexpected situations can arise. However, these challenges can be viewed as opportunities for growth and learning. With careful planning and a positive mindset, the rewards of traveling far outweigh the difficulties.
The word "immersing" in paragraph 2 is closest in meaning to:
Xác định ý đúng: Công dụng thứ tư của mạch điều khiển tín hiệu là gì ?
Đọc đoạn trích sau đây và trả lời câu hỏi.
“Trận thắng trên sông Bạch Đằng là cơ sở cho việc khôi phục quốc thống. Những chiến công đời Đinh, Lê, Lý, Trần sau này còn nhờ vào uy danh lẫm liệt ấy để lại”.
(Quốc sử quán triều Nguyễn, Khâm định Việt sử thông giám cương mục, Tập 1, Nxb Giáo dục, HN, 1998, tr.211)
Nội dung nào sau đây phản ánh đúng ý nghĩa của “việc khôi phục quốc thống” đối với lịch sử Việt Nam được đề cập trong đoạn trích?
Phương trình đường tròn có tâm thuộc đường thẳng \(\Delta: x-2 y=0\), tiếp xúc với đường thẳng \(\Delta^{\prime}: 2 x-y+2=0\) đồng thời đường tròn đi qua điểm \(M(1; 3)\) là:
Muốn thể hiện vùng trồng thuốc lá của nước ta, có thể sử dụng phương pháp gì?
Tế bào vi khuẩn có kích nhỏ và cấu tạo đơn giản giúp chúng có đặc điểm như thế nào?
Thiên hoàng Minh Trị tiến hành cải cách trong hoàn cảnh nào?
Read the passage carefully
1. Millions of people are using cellphones today. In many places, it is actually considered unusual not to use one. In many countries, cellphones are very popular with young people. They find that the phones are more than a means of communication - having a mobile phone shows that they are cool and connected.
2. The explosion in mobile phone use around the world has made some health professionals worried. Some doctors are concerned that in the future many people may suffer health problems from the use of mobile phones. In England, there has been a serious debate about this issue. Mobile phone companies are worried about the negative publicity of such ideas. They say that there is no proof that mobile phones are bad for your health.
3. On the other hand, medical studies have shown changes in the brain cells of some people who use mobile phones. Signs of change in the tissues of the brain and head can be detected with modern scanning equipment. In one case, a traveling salesman had to retire at young age because of serious memory loss. He couldn't remember even simple tasks. He would often forget the name of his own son. This man used to talk on his mobile phone for about six hours a day, every day of his working week, for a couple of years. His family doctor blamed his mobile phone use, but his employer's doctor didn't agree.
4. What is it that makes mobile phones potentially harmful? The answer is radiation. High-tech machines can detect very small amounts of radiation from mobile phones. Mobile phone companies agree that there is some radiation, but they say the amount is too small to worry about.
5. As the discussion about their safety continues, it appears that it's best to use mobile phones less often. Use your regular phone if you want to talk for a long time. Use your mobile phone only when you really need it. Mobile phones can be very useful and convenient, especially in emergencies. In the future, mobile phones may have a warning label that says they are bad for your health. So for now, it's wise not to use your mobile phone too often.
Choose an option (A, B, C, or D) that best answers each question:
According to the passage, what can be inferred about cellphones?
Read the following passage about endangered languages and mark the letter A, B, C or D on your answer sheet to indicate the best answer to each of the following questionsfrom 31 to 40.
[I] Social media has become a dominant force in modern communication, offering a range of benefits and challenges. [II] It has revolutionized the way people interact, share information, and even form relationships. [III] While these platforms offer opportunities for connection and expression, they also have their drawbacks. [IV] For instance, excessive use of social media has been linked to a range of negative effects, including mental health issues, social isolation, and decreased productivity. [V] However, when used responsibly, social media can also offer a variety of positive outcomes, such as the ability to stay connected with loved ones, network professionally, and access valuable information and resources.
One of the major benefits of social media is its ability to keep people connected. For example, individuals who live far apart can maintain close relationships through regular communication on these platforms. Social media also facilitates professional networking, allowing users to connect with potential employers or clients, and enabling companies to promote their products and services to a global audience. Additionally, platforms like Facebook, Twitter, and Instagram provide a space for people to share ideas, opinions, and creative work, fostering a sense of community and collaboration.
Despite these advantages, there are serious concerns about the negative impact of social media, particularly on mental health. Studies have shown that excessive social media use can contribute to feelings of anxiety, depression, and loneliness. This is often attributed to the unrealistic portrayals of life that are commonly shared on these platforms, leading to comparisons that can make individuals feel inadequate or left out. Furthermore, constant exposure to negative news or online bullying can exacerbate these feelings and contribute to long-term psychological stress.
Another issue with social media is its potential to distract people from their daily responsibilities. With notifications constantly popping up and endless streams of content to scroll through, individuals may find it difficult to focus on tasks such as work, school, or personal obligations. This can result in decreased productivity and a lack of attention to important matters.
Ultimately, the impact of social media depends on how it is used. If individuals are mindful of their usage patterns and take steps to limit their time on these platforms, they can enjoy the benefits of staying connected and informed without the negative consequences. Parents, educators, and mental health professionals can also play a role in helping young people develop healthy habits and manage their social media use effectively.
Which of the following best summarizes paragraph 3?
Read the following passage about the benefits of learning a foreign language and mark the letter A, B, C, or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 18 to 22. (1,25 point)
Learning a foreign language has become increasingly important in our globalized world. It not only opens up new opportunities for communication and cultural exchange but also (18) ___________ in a highly interconnected and diverse society. Despite these advantages, there are still challenges involved in learning a new language, especially in (19) ___________ to practice every day.
Many educational institutions are incorporating foreign language programs (20) ___________. These programs are designed to enhance students' cultural awareness and improve their career prospects. For example, (21) ___________ in various job markets, where employers value language skills. However, it is essential (22) ___________ to meet the needs of diverse learners.
Phát biểu nào dưới đây không đúng về các loại thực vật?
Bộ phận nào của virut bám đặc hiệu vào thụ thể của tế bào chủ?
Đâu là nơi diễn ra các quan hệ thoả thuận giữa người sử dụng lao động và người lao động về tiền lương, điều kiện làm việc trên cơ sở hợp đồng lao động?
Cơ cấu dân sô thể hiện được tổng hợp tinh hình sinh tử, tuổi thọ, khả năng phát triển dân số và nguồn lao động của một quốc gia là gì?