An antifreeze（防冻剂）is a liquid that is added to water to keep it from freezing. When water freezes and turns to ice, it expands. The force of water expanding is so great that it will break the hardest metal. Water is used in car engines 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 antifreezes are necessary.
Water freezes at the 0℃: the usual kind of antifreeze will not freeze until the temperature is 40℃ below zero. A mixture of 5 parts of water and 4 parts of antifreeze will prevent freezing at 18℃ below zero; 4 parts of water and 5 parts of antifreeze reduce this to 22℃ below zero.
Alcohol（酒精）is a good antifreeze, but when the car is running it becomes hot and the alcohol boils away, so it must be replaced very often. Most people use antifreezes that do not boil away when the engine is running. There are several chemicals that do this. One of the most popular is called ethylene glycol（乙二醇）, which is sold under various trade names such as Preston and Zerex.
64. Antifreezes are useful in that they _____.
A. keep the alcohol from boiling away B. can prevent ice from melting
C. keep water liquid in cold weather D. can raise the freezing point of water
65. The text is written _____.
A. to help to sell antifreezes B. to explain what antifreezes are
C. to compare ethylene glycol with alcohol D. to tell how to choose the best antifreeze
66. Preston and Zerex are _____.
A. trade names of two kinds of alcohol B. popular brands（商标）of car engines
C. inventors of ethylene glycol D. liquids used for car engines