问题补充：
These achievements without the contribution of Qian Xuesen, a key leader of the New Chinas 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
答案：
(答案→)A. would have been unthinkable
B. would not be unthinkable
C. would be unthinkable
D. would not have been unthinkable
解析：（本题考查虚拟语气。题干句子中“without the contribution of Qian Xuesen”表示与过去事实相反的虚拟语气，谓语动词要用“would（not）}lave done’。）
