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:hina's nuclear, missile and so on /T
D: would not have been unthinkable
B: would not be unthinkable
C:hina's nuclear, missile and so on /T
D: would not have been unthinkable
正确答案是：
