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
答案:A
(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'’。)