been the major concern of the US government of the last 50 years.
been more than doubled over the last half century.
reduced dramatically.
been the main source of export for US agriculture.
第1题:
John told us that by the end of the year they _____ together for thirty years.
A. would have been living
B. would have lived
C. would have been lived
D. will have been living
第2题:
His parents _______ the US for ten years.
A、have been
B、have gone to
C、have been to
D、have been in
第3题:
A. have taught
B. have been taught
C. has taught
D. had been taught
第4题:
第5题:
第6题:
A has been caused
B had been caused
C will be caused
D will have been caused
第7题:
Had Paul received six more votes in the last election, he ________ our chairman now.
[A] must have been
[B] would have been
[C] were
[D] would be
第8题:
A. has been caused
B.have been caused
C.will be caused
D.will have been caused
第9题:
第10题: