| 7.Duck have been domesticated for many centuries____ commercially for their meet and eggs. 
 A.raised. 
 B.and are raised. 
 C.raised as 
 D.are raised. 
 答案:B. A为什么错,过去分词作状语也说得通呀.是不是centuries后面有一逗号的话,A就对了? 
 
 8. According to the fossil record of carnivore families, felines developed more rapidly than ___ 
 A. other carnivore families were 
 B.other carnivore families 
 C. there were other cannivore families. 
 D. so did other canivore families. 
 B对没错.但D好象也可以啊. 
 
 9. Computer graphics are ___ programmed and operated by human beings. 
 A.the computer generates pictures. 
 B.computers generated pictures. 
 C. pictures generate computers 
 D pictures generated by a computer. 
 答案应该是D吧? 
 
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