Một số amine no, đơn chức, mạch hở, trong phân tử có phần trăm khối lượng nitrogen bằng 23,73%. Có bao nhiêu chất là đồng phân tác dụng được với dung dịch nitrous acid (HNO2) ở nhiệt độ thích hợp sinh ra alcohol và khí nitrogen?        

Which of the following best summarises the passage?

Dòng điện định mức của aptomat phù hợp để cấp điện cho máy giặt có công suất 2000 W (hệ số cosφ = 0,8) và điện áp 220 V là

Hai vật được thả rơi tự do đồng thời từ hai độ cao khác nhau h₁ và h₂. Khoảng thời gian rơi của vật thứ nhất bằng một nửa khoảng thời gian rơi của vật thứ hai. Bỏ qua lực cản của không khí. Tỉ số các độ cao $\dfrac{h_1}{h_2}$ bằng

Read the following advertisement/school announcement and mark the letter A, B, C, or D on your answer sheet to indicate the correct option that best fits each of the numbered blanks from 10 to 15.

WANT TO BE A TOUR GUIDE?

Are you over 18? Are you interested (10) _______ travelling and exploring different cultures?

Apply to ABC Vocational School. We provide tour guide training courses all year round:

- No (11) _______ qualifications needed

- Low cost

- Apprenticeships provided

Contact (12) _______:

- Email: abcxyz@web.mail

- Address: 100 Olden Street, Ballack Clava

Read the following passage about managing change 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. 

Growing up in Athens, Greece, Lydia Borsi remembers feeling tested when she tried to deal with mental health issues. Borsi says she had been seeing a therapist for anxiety. But she notes that people in Greece do not openly discuss mental health issues, which also get little attention in general healthcare services. “It was a lot more secretive. And people thought that I was a lot more unique,” Borsi said.

That all changed in 2017 when she moved to the United States to study at the University of Rochester in Rochester, New York. “When I came here, I really liked that people were not afraid to speak up about mental health and say that it’s important,” she said. The university was very supportive of her needs and offered plenty of information. She also became involved with a school group called Active Minds that helps students deal with mental health issues. [A]

Then due to the spread of the novel coronavirus, the University of Rochester had to move all its classes and some of its mental health resources online. Luckily, Borsi was able to connect with a mental health expert outside the school, in the local community. [B]

But as many of her American friends returned home, Borsi was stuck. Greece had succeeded in limiting the spread of the virus within its borders, but flights there from the U.S. are barred until July. Also, the health crisis has put her plans to seek admission to medical school in Britain on hold. [C] And she is not alone.

[D] In April, Active Minds launched a survey of over 2,000 students at U.S. colleges and universities. The study found that over 80 percent of those asked said the coronavirus crisis had negatively affected their mental health. One in five said it has affected them severely.

Laura Horne, chief program officer at Active Minds, says the findings are especially troubling given that the crisis is only going to make it harder for colleges and universities to help these students. “Colleges and universities had to pivot rather quickly to respond to COVID-19 and figure out all facets of university life, including mental health services. Now they have to figure out how to communicate with students,” Horne said.

Frank Chen is a Houston, Texas-based psychiatrist who has worked with college-age young adults. He points out that individuals at that age are in an important stage of their mental development. And college can be a difficult experience for students with or without mental health issues, as they balance work, studies, and personal relationships. Adding a major world event, like the spread of the coronavirus, makes it very difficult to predict what the long-term psychological effects might be. “I don’t think that there’s another event in the history of the people who are alive now that can really measure up to this,” said Chen.

Why did the writer start the article with Borsi’s story in the first paragraph?

Cho mệnh đề: "Nếu $n$ là một số nguyên tố lớn $3$ thì $n^2 + 20$ là một hợp số". Mệnh đề nào sau đây tương đương với mệnh đề đã cho?

Giá trị của biểu thức: P = cos0° + cos1° + cos2° + ... + cos178° + cos179° + cos180° thuộc khoảng nào sau đây?

Nguyên tử nguyên tố X có tổng số hạt cơ bản là 40. Trong đó, số hạt mang điện nhiều hơn số hạt không mang điện là 12 hạt. Số proton trong nguyên tử nguyên tố X là

Đâu là ý đúng: Bào quan dạng bong bóng trong tế bào chất của tế bào động thực vật là gì?

Ô tô là phương tiện giao thông đường bộ có:

Một thang máy có khối lượng 1300 kg được kéo lên theo phương thẳng đứng bằng dây cáp nối với một động cơ như hình 1. Hình 2 là đồ thị biểu diễn sự biến thiên tốc độ \(\text{v}\left( \text{m}/\text{s} \right)\) của thang máy theo thời gian \(\text{t}\left( \text{s} \right)\) (lấy \(\text{g}=9,8\text{ }\!\!~\!\!\text{ m}/{{\text{s}}^{2}}\)).

Lực căng trung bình của dây cáp trong khoảng thời gian từ giây thứ 40 đến giây thứ 50 là bao nhiêu?

Read the following passage about home schooling in the UK 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.

Full-time education in the UK is compulsory from the age of five to sixteen, but this doesn’t have to be in a school. Around 50,000 children are educated at home. This is called ‘homeschooling’.

 Parents take their children out of school for different reasons, like illness and the need for special care, or because the distance to the nearest school may be too far. Some children are simply unhappy at school. Whatever the reason, they’re allowed to study at home, although inspectors regularly check how they are getting on.

 Hayley and Jenny haven’t been to school for two years but they haven’t neglected their studies. Their mother worked out strict timetables for them, with hourly lessons for each day. She’s responsible for teaching them Maths, English, History and French. Their father teaches them Science and Geography. They study all the other school subjects online. ‘We have lessons with Dad in the evenings and at weekends,’ explains Hayley.

 The family’s home is in a remote part of Wales. ‘The girls were fine at school but they spent so much time getting to school, they were too tired to learn, says their mother, Julia”. ‘We had a family conference and in the end we decided to try homeschooling. So far, it’s been a big success, but the girls know that if they want to go back to school at any time, we’ll let them. We follow the normal school program of lessons, and they will take all the normal school exams.’

 There are disadvantages too, of course. ‘Social isolation is something I worry about,’ says Julia. They both seem happy and well-adjusted, but they haven’t really got friends who live locally. But in the summer holidays they go away on trips to summer camps, where they have no trouble mixing with people and making friends.’

In which paragraph does the writer describe the daily routine of Hayley and Jenny?