单选题
By the time of 1969, there
were
many space explorations.
A、
have been
B、
must be
C、
had been
D、
must have been
【正确答案】
C
【答案解析】
[解析] 根据时间状语by the time of 1969可判断本句表示过去某时刻前发生的动作或状态，应用过去完成时；因此答案为C。
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