题目

下列微粒结构示意图中，表示阳离子的是（    ）     答案：CAntifreeze 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．1.people use ________ to keep car engines cool．A. antifreeze B. water C. alcohol D. ethylene glycol.2.The usual kind of antifreeze freezes at ________．A. 0℃ B. －18℃ C. －22℃ D. －40℃3.We use antifreeze in order to ________．A. keep alcohol in waterB. stop ice from becoming waterC. make the freezing point of water lowerD. raise the freezing point of water4.Besides alcohol，________ is another kind of popular antifreeze．A. water B. ethylene glycol C. any chemical D. any mixture5.The text is written to ________．A. tell us what antifreeze isB. make people buy antifreezeC. tell us that cars need antifreezeD. show us how to protect car engines