Antifreeze is a liquid(液体) that is added to water to keep it from freezing． When water freezes and turns to ice，it expands(膨胀)．The force of water expanding is so great that it will break the hardest metal．Water is used in car engines(发动机) to keep them cool while they run，and if this water is allowed to freeze in winter it can break the iron block of the engine．That is why antifreeze is necessary．
Water freezes at 0℃；the usual kind of antifreeze will not freeze until the temperature is－40℃．A mixture(混合物) of five parts of water and four parts of antifreeze will prevent freezing at－18℃；four parts of water and five parts of antifreeze reduce this to －22℃．
Alcohol is a kind of good antifreeze，but when the air is running it becomes hot and the alcohol boils away，so it must be changed very often．Most people use antifreeze that does not boil away when the engine is running．There are several chemicals that do this．One of the most popular is called ethylene glycol．
【小题1】people use ________ to keep car engines cool．

根据对话内容，在空白处填写适当的话语（话语可能是一个句子，也可能是一个短语或一个词），使对话完整。

（Thomas was very nervous before going to have a meal at his friend’s house.）

Mr. Lee: Thomas, you look worried. 1．____________?

Thomas: I’m going to have a meal at a Korean friend’s house and I don’t know what I am supposed to do.

Mr. Lee: I have been to Korea twice and I know some Korean table manners.

Thomas: Oh, that’s great! I’ve heard that it’s OK to make noise when you eat in Korea.

Mr. Lee: I guess so, but it depends. When you eat 2．____________, for example, you have to make noise.

Thomas: What do you mean “have to”?

Mr. Lee: It’s said that noodles taste better that way. It shows that you 3．_____________.

Thomas: That sounds interesting.

Mr. Lee: At other times try to eat as quietly as possible. It’s not polite to talk while chewing food.

Thomas: I see. 4． _____________?

Mr. Lee: Yes, they use chopsticks for most foods. But for rice and soups they use spoons.

       Remember: Never hold both at the same time.

Thomas: Is it OK that I eat the food fast and leave the table early?

Mr. Lee: Not at all. In Korean culture, older people are highly respected（尊敬）, you must wait for the elders to hold their spoons first. And you should eat neither too fast nor too slowly. You should keep pace（速度）with the elders. When the elders finish the meal, you can get up together.

Thomas: Oh, that’s quite different from ours. Thank you so much for 5．__________.

Mr. Lee: My pleasure. Please enjoy your meal.