Trên mặt chất lỏng có hai nguồn dao động S₁ và S₂ cùng phương, cùng phương trình dao động $u=a\cos2\pi ft$. Bước sóng là $\lambda$. Khoảng cách giữa hai điểm liên tiếp trên đoạn S₁S₂ dao động với biên độ cực đại là

Cho những thông tin trong bảng sau đây:

Cơ thể động vật không lấy từ môi trường sống chất nào sau đây?

Sau Chiến tranh thế giới thứ hai, vùng Tây Âu thuộc phạm vi ảnh hưởng của:

Read the following passage 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 31 to 40.

Biting into a ripe, juicy fruit brings a smile to many people’s faces. But eating that same fruit a week before it is ripe probably wouldn’t be as enjoyable! Unripe fruits are often hard and bitter, but that serves a purpose. The hard exterior of an unripe fruit protects the developing seed inside. After a seed fully develops inside the fruit, the fruit changes color, softens, and gets sweeter to become more attractive to animals and humans. These organisms eat the fruit and spread its seeds, ensuring the plant’s survival and regrowth.

But how does a fruit ripen? The ripening process involves many complex chemical reactions. When a fruit ripens, it goes through a chemical change. A chemical change happens when bonds within molecules break, and the atoms that once formed them regroup into new molecules. Chemical changes are irreversible. Once a fruit ripens, it cannot become unripe again.

One molecule responsible for this chemical change is ethylene. Ethylene (C2H4) is a colorless gas made up of carbon and hydrogen atoms. (I). It is a naturally occurring molecule in the atmosphere. (II). It is also an important plant hormone. (III). Plants release ethylene through the growing tips of roots, flowers, and ripening fruit. (IV). Although ethylene serves other purposes in plants, one of its main purposes is to trigger the chemical reactions that cause fruits to ripen. As the fruit matures, oxygen in the air helps stimulate the production of ethylene. This ethylene production is a signal that begins fruit ripening. For that reason, unripe fruits have low levels of ethylene, while ripe fruits have higher levels of ethylene. Most fruits produce ethylene and respond to ethylene in the atmosphere.

Although fruits require ethylene to ripen, different types of fruits respond to this molecule in two distinct ways: non-climacteric fruits and climacteric fruits. Non-climacteric fruits do not ripen after harvesting. They produce very little ethylene of their own. Climacteric fruits, on the other hand, continue to ripen after they are picked. These fruits produce a large amount of ethylene. Climacteric fruits can also speed up the ripening process of other fruits nearby since they release high levels of ethylene into the air.  

According to the passage, which of the following is NOT a factor in fruit ripening?

Để lấy mẫu áp dụng cho vùng ảnh cần tẩy xóa, nhấn giữ phím nào khi nháy chuột vào một điểm ảnh?

Các chi tiết nào dưới đây cùng với xilanh và đỉnh piston tạo thành buồng cháy của động cơ?

Chọn ý đúng nhất: Theo phương pháp chiếu góc thứ nhất, vật thể đặt trong góc tạo bởi mấy mặt phẳng?

Hoạt động con người tạo ra sản phẩm vật chất và tinh thần, đáp ứng nhu cầu của đời sống xã hội được gọi là gì?

Các nguyên tố hóa học được sắp xếp vào bảng tuần hoàn dựa theo nguyên tắc

Mệnh đề nào sau đây đúng?

Đảo nào nằm ở phía Bắc của Nhật Bản?

Cho hình lập phương $ABCD.A^{\text{'}}{B}^{\text{'}}{C}^{\text{'}}{D}^{\text{'}}$ cạnh a. Tính khoảng cách giữa đường thẳng AD và mặt phẳng $\left(BC{D}^{\text{'}}{A}^{\text{'}}\right)$? 

Ngoài hệ điều hành Android, Andy Rubin còn dành mối quan tâm đến cả phát triển những lĩnh vực khác. Một trong số đó là …?

Một vật chuyển động trong \(3\) giờ với vận tốc \(v\) (km/h) phụ thuộc thời gian \(t\) (h). Trong khoảng thời gian \(1\) giờ kể từ khi bắt đầu chuyển động, vận tốc của nó là \(v=-\frac{5}{4}{{t}^{2}}+5t+4\); trong khoảng thời gian còn lại vật chuyển động đều.

Nhà nước cần làm gì để khắc phục, hạn chế nhược điểm của cơ chế thị trường?

Bản thân em là chủ thể sản xuất khi

Read the following passage about the impact of social media on mental health 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 31 to 40.

          [I] In recent years, social media platforms have become a central part of daily life, offering users countless ways to connect, share, and communicate. [II] While these platforms offer many advantages, experts have noted rising concerns about their effects on mental health, particularly among young people (Smith & Anderson, 2018). [III] Studies reveal that excessive social media use can contribute to feelings of anxiety, depression, and loneliness, despite its intention to promote connection and social interaction (Twenge & Campbell, 2019). [IV]

          A primary reason for these mental health concerns is the tendency for social media users to compare themselves to others. Platforms like Instagram and Facebook often highlight idealized lifestyles, leading users to feel inadequate about their own lives. Additionally, the constant notifications and messages contribute to a "fear of missing out," or FOMO, which keeps individuals in a cycle of checking their phones, often reducing the quality of sleep and overall well-being.

          There is also a growing body of research suggesting a link between social media use and decreased attention spans. When users frequently switch between apps and notifications, their ability to focus for extended periods may diminish (Rosen, 2019). This shift in attention can interfere with productivity, especially in academic and professional settings, where sustained focus is essential.

          Addressing these challenges requires a multi-faceted approach. Some mental health professionals suggest limiting screen time and setting boundaries, such as "device-free" hours before bedtime. Others recommend engaging in offline activities, like reading or exercising, to reduce dependence on social media and build healthier habits. According to psychologists, such strategies can enhance mental resilience and allow for more meaningful, balanced relationships (Robinson & Smith, 2020).

Where in paragraph I does the following sentence best fit?

Young people are particularly affected due to their high engagement with these platforms.