问题
These achievements_______ without the contribution of Qian Xuesen, a key leader of the New China’s nuclear, missile and so on．
A:would have been unthinkable
B:would not be unthinkable
C:would be unthinkable
D:would not have been unthinkable
B:would not be unthinkable
C:would be unthinkable
D:would not have been unthinkable
正确答案是：
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