1、be known as +n. ; be known to do ; be known for doing ;排除BDE;
2、the number of单数， are known复数错误，排除DE；
3、to become extinct没有 to extinction更优。

be known as +n. 正确 排除BE
be known to do sth. 正确
be known for doing 错误 排除C
D force后面缺少宾语
force sb to do sth，强迫某人作某事；force sb to sth，强迫某人进入某种状态

for anybody who wants to know the answer, --- by Ron

probably the easiest way to go here is to remember this as an idiomatic usage of the construction "known to". if the action is in the present, then you use "known to VERB"; if the action is in the past, then you use "known to have VERBed". as far as i know, these are the only two possible forms.
"known as" is incorrect unless it is followed by a noun:
Albert Einstein made his living as a patent clerk, but he was far better known as the original proponent of the theory of relativity.
--> correct (note that "proponent" is a NOUN)

1、be known as +n. ; be known to do ; be known for doing ;排除BDE;
2、the number of单数， are known复数错误，排除DE；
3、to become extinct没有 to extinction更优。

Ron：
known as is used with nouns: al capone was known as a gangster rather than as a tax cheat, but he was ultimately imprisoned only on charges of tax evasion.
with verbs, you have to use 'known to infinitive' or 'known for gerund'.

be known as +n.
be known to do sth. 对 be known for doing sth,错

m
human are know to do /have done
force + to+n

d that 使用wordy
Humans are known to have forced plant and animal species to extinction.
force 。。to+n。
还是选最短的

be known/believed to do sth，被认为作了某事，被动里可以+to
force sb to do sth，强迫某人作某事；force sb to sth，强迫某人进入某种状态，如：Health forced him into early retirement. 从语法上来说，to是介词，+doing或+名词都可以

E项除了固定搭配be known to do错了以外，还有问题是把species做了主语，但已知的应该是人是species 灭绝

"known as" is incorrect unless it is followed by a noun:
Albert Einstein made his living as a patent clerk, but he was far better known as the original proponent of the theory of relativity.
--> correct (note that "proponent" is a NOUN)

定语从句还原是：
Humans are known to have forced plant and animal species to extinction.

错选E，be known as doing 错误的idiom，正确的是be known as + n.

D化简后：The number ( ) that humans forced to become extinct，无法表意。

"known as" is incorrect unless it is followed by a noun:
Albert Einstein made his living as a patent clerk, but he was far better known as the original proponent of the theory of relativity.
--> correct (note that "proponent" is a NOUN)

a正确，somebody be known to do something
b, be known as + noun
c, 意思错误了，原意应为人们过去force animal to become extinct, c的意思是 people are forcing animal to become extinct.
d, that 使用错误
e, 同c

be known to have done sth. 被知晓过去做过某事
be known for doing sth. 被知晓做某事
be known as + n.
D：are known that 表达wordy
E： be known as doing 错误的idiom，正确的是be known as + n.

be known to have done sth. 被知晓过去做过某事
be known for doing sth. 被知晓做某事
be known as + n.
D：are known that 表达wordy
E： be known as doing 错误的idiom，正确的是be known as + n.

定语从句还原是：
Humans are known to have forced plant and animal species to extinction.

analogies:
the island's natives are known for stealing tourists' money, passports, and jewelry. --> these things go on today
the island's natives are known to have stolen tourists' money, passports, and jewelry. --> not necessarily still happening, but it has happened at some point