Tet is one of the most important festivals in my country. It's a big holiday that celebrates the arrival of spring in Viet Nam every year. It usually lasts about seven days. There are lots of popular customs of Vietnamese people on Tet holiday. For example, they often visit their relatives, friends anh temples. Some people visit the graves of their ancestors in their homeland. Before Tet holiday begins, people decorate their house carefully to have a wonderful time with their family. Furthermore, special Tet food such as Chung cake, steamed sticky rice and boiled chicken can play an important role in Vietnam. Perhaps, Tet is the time when members of family can gather to chat or have meals together. In conclusion, Tet is the essential part in Vietnam.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

         It is very important to have healthy teeth. Good teeth help us to chew our food. They also help us to look nice. How does a tooth go bad? The decay begins in a little crack in the enamel covering of the tooth. This happens after germs and bits of food have collected there then the decay slowly spreads inside the tooth. Eventually, poison goes into the blood, and we may feel quite ill. How can we keep our teeth healthy? Firstly, we ought to visit our dentist twice a year. He can fill the small holes in our teeth before they destroy the teeth. He can examine our teeth to check that they are growing in the right way. Unfortunately, many people wait until they have toothache before they see a dentist. Secondly, we should brush our teeth with a toothbrush and fluoride toothpaste at least twice a day-once after breakfast and once before we go to bed. We can also use wooden toothpicks to clean between our teeth after a meal. Thirdly, we should eat food that is good for our teeth and our body: milk, cheese, fish, brown bread, potatoes, red rice, raw vegetables and fresh fruit. Chocolate, sweets, biscuits and cakes are bad, especially when we eat them between meals. They are harmful because they stick to our teeth and cause decay.

Sweets are harmful because they may make our teeth________

A. crack     

B. decay      

C. painful    

D. black