亲们,

亲们,
1'Many people agree that ____knowledge of English is _____must in ______international trade today.(a;a;不填）主要讲一下第一空.
2'No one has yet succeeded in explaining the _______of how life began.
A.cause B.problem C.reason D.puzzle 为什么不能选C?
3'_________you find high wages you will generally find high prices.
A.When B.Where C.Since D.Whether答案是B
4'China's entry into the WTO has as great an influence upon China as________.
A.the United States B.that of the United States C.it does upon theUnited States D.it has to theUnited States