A less 修饰不可数，且用less的话，前面要用there is
B 正确，没选是因为缺少一个as，实际上是省略用法
C amount修饰不可数名词，不能用来修饰4,000（drive-ins）这个可数的量
D the number指代不清；the amount指代不清，只能修饰不可数名词；the number is less没有问题，less和smaller都可以修饰数字。
E it没有指代对象，that amount指代4,000 drive-ins错。
Ron:that doesn't work, because "they know" isn't in the first part. if a construction can be omitted, then the same construction should exist elsewhere in the sentence. here, it doesn't; the omitted portion would be assumed to correspond to "demographers have to know", which doesn't make any sense.
题干想表达的意思是他们必须比现在知道的更多，但是如果省略they do意思就变成了必须比不得不知道的知道的更多，不合理，排除AE
#announce+从句可以不加that！！#
A中时态错误
B时态错误，account for意思相反
D idiom错误，应该是announce +(that)+Clause/announce+noun/announce sth to sb/announce to sb sth.
E 时态错误，having done累赘
Take away：英语语法规定，当谓语动词的意思是“建议、命令、要求”时，由于身后的从句中的谓语动词必须用原型（通常需要省略should）。
Split#1：选项B中 were doing 时态错误，去掉。选项D中，for不对，应该为as，去掉。
Split#2：选项A和E对比，E用了倒装，没必要，去掉选项E
Split#3：选项对比，一个reform prisoners一个reform them，指代不清，去掉选项A
(1) Digging in sediments in northern China, scientists have gathered evidence suggesting that complex life-forms emerged much earlier than previously thought.
(2) A surge in new home sales and a drop in weekly unemployment claims suggest that the economy might not be as weak as some analysts previously thought.
(3) Even though more money was removed out of stock funds in July than in any other month since October 1987, sales of fund shares in July were not as low as what an industry trade group had previously estimated.
感受一波
1) 下划线最后剩了televised nationwide, 提示观察划线与其是否搭配。C/E中in the hearings on the impeachment of President Richard Nixon, which中，which如果是was修饰的是impeachment而不是hearings，impeachment作为legal procedure不能被televised。
2) 观察选项发现有was/were的区别。A中是倒装句，was主语为she没问题，但后面it was中it指hearings错误、was错误，E中hearings应该是which were
3）then与later不能重复用
4）D中的comma+V-ing不能作impeachment的定语，是整个句子的adverb modifier
A: we want different tenses, because one of these things is something that's permanently true (it makes burrowing difficult) while the other represents only the potential that something could happen (it could cause tunnels to collapse).
this simpler sentence, with the same construction, should be easier to understand:
Frank is extremely angry and could start yelling or punching the wall at any moment.
D: as...as to - no such structure; so...as to - the right structure
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which修饰前方最靠近的那个名字，所以AB，which都修饰了1999.