答案:三分之二
解析:解析:
A. f(1)-f(0)
B. 2[f(1)-f(0)]
C. 2[f(2)-f(0)]
D.
解析:解析:
A. must be
B. could be
C. must have been
D. should have been
解析:解析:对过去推测,情态动词后接现在完成时。
A. that
B. which
C. /
D. all of the above
A. was it
B. were they
C. are they
D. is it
解析:解析:news 当消息讲是不可数名词
A. that
B. which
C. what
D. it
A. would destroy
B. would be destroyed
C. would have destroyed
D. would have been destroyed
解析:解析:broke out(break out) 爆发