I DID NOT ANSWER THE DOOR EVEN THOUGH I KNEW IT WAS MY FRIEND.A.UNLESS...

Câu 30:I did not answer the door even though I knew it was my friend.A.Unless I knew it was my friend, I would not answer the door.B.I knew it was my friend, but I did not answer the door.C.Only when I answered the door did I knew it was my friend.D.I answered the door since I knew it was my friend.Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate thecorrect answer to each of the questions.Millions of people are using cell phones today. In many places, it is actually considered unusualnot to use one. In many countries, cell phones are very popular with young people. They find that thephones are more than a means of communication - having a mobile phone shows that they are cool andconnected.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 ofmobile phones. In England, there has been a serious debate about this issue. Mobile phone companies areworried about the negative publicity of such ideas. They say that there is no proof that mobile phones arebad for your health.On the other hand, medical studies have shown changes in the brain cells of some peoplewho use mobile phones. Signs of change in the tissues of the brain and head can be detected with modernscanning equipment. In one case, a travelling salesman had to retire at young age because of seriousmemory 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, fora 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. High- tech machinescan detect very small amounts of radiation from mobile phones. Mobile phone companiesagree 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 reallyneed 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 notto use your mobile phone too often