Dưới đây là tài liệu 30 Câu trắc nghiệm tiếng Anh (kèm lời giải thích) giới thiệu tới các bạn về cấu trúc ngữ pháp và những bài tập trắc nghiệm củng cố kiến thức về mệnh đề danh ngữ; bỏ đại từ quan hệ khi chúng làm chủ ngữ. Đặc biệt ở cuối tài liệu với mỗi bài tập trắc nghiệm đề có những giải thích chi tiết cho việc lựa chọn đáp án đúng. | Millions of people are using cell-phones today. In many places, it is actually considered unusual not to use one. In many countries, cell-phones 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. The explosion ( sự bùng nổ ) 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 ( bằng chứng ) that mobile phones are bad for your health. 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. What is it that makes mobile phones potentially harmful? The answer is radiation ( sự bức xạ ). High-tech machines can detect (dò tìm) 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. 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 ( tình trạng khẩn cấp ). 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.
