By the time of 1969, there were many space
题型:单项选择题
问题:
By the time of 1969, there were many space explorations.
A.have been
B.must be
C.had been
D.must have been
By the time of 1969, there were many space explorations.
A.have been
B.must be
C.had been
D.must have been