It was in 1969 ________ two Americans went to the moon by spaceship.

It was in 1969 ________ two Americans went to the moon by spaceship.

A.that

B.before

C.when

D.since

答案及解析： A

解析：

该句为强调句型，强调了时间状语in 1969。in 1969为独立存在且意义完整的一部分，即去掉It was和空白处，句子意义不变，只是结构发生了变化。