【求助】PREP07-2第83题

小唯唯

83. (28949-!-item-!-188;#058&004110)  E 01:03  
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
答案是A。
我不太明白这句话的意思，因为PREP笔记在解释时说“句子结构：The number of… is over 800.为句子主结构。划线部分为句子限定性定语从句，修饰species，表示人们知道的已经绝种的动物和植物的数量为800种。在定语从句中，that指代plant and animal species，做从句have forced的宾语，而不是从句主语。从句还原之后正常语序形式为：humans are known to have force that (指代plant and animal species)to extinction…”

这句话不是应该是“已经知道的被人类逼死的。。。。有800种”么？不然那个force怎没解释呢？
另外：be known to do something为正确的习语 这个be known to do 是什么意思呀

毛毛carina

恩~~就是表达目前已知道的被人类逼绝迹的动植物种类数量为800    笔记上只是说明一个大意，肯定不可能每句话都翻译完整的。

小唯唯

恩~~就是表达目前已知道的被人类逼绝迹的动植物种类数量为800    笔记上只是说明一个大意，肯定不可能每句话都翻译完整的。

-- by 会员 毛毛carina (2011/3/27 15:16:03)

那那be known to do sth.的意思就是“已经知道做了XX”是么？