1.Nebraska has floods in some years, ___.
A.in other drought
B.droughts are others
C.while other droughts
D.others in drought
2.___ all behavior is learned behavior is a basic assumption of social scientists.
C.It is nearly
3.Sir Dennis, who is 78, has made it known that much of his collection ___ to the nation.
B.is to leave
D.is to be left
4.I hope that by posting the letter now at midday, I shall ensure ___ it before the weekend.
C.you to receive
D.your having received
5.She has taken great pains to conceal her emotions, and thereby made them ___ conspicuous.
A.all the more
B.all the much
1.[A]【解析】在并列从句中，为避免重复，相同的成分可以省略，原句为：“Nebraska has floods in some years, and Nebraska has drought in other years.”。
5.[A]【解析】all the more为固定搭配，意为“更加”。