标题: PREP SC 一道题纠结，求助 [打印本页] 作者: azhongzhong 时间: 2011-9-11 16:55 标题: PREP SC 一道题纠结，求助 The number of plant and animal species that humans are known to have forced to extinction in the last half millennium is over 800.
A.humans are known to have forced to extinction
B.humans are known as having forced to become extinct
C.humans are known for forcing to become extinct
D.are known that humans forced to become extinct
E.are known as having been forced to extinction by humans 这道题我选的E，答案是A，为何A比E好？