What we used to think impossible now does seem possible. A．is B．was C．has been D

What we used to think ______ impossible now does seem possible.

       A．is                         B．was                    C．has been              D．will be

试题答案

B．

解析：本题考查考生对于主谓一致和事态的使用能力。由used to可以看出应用过去时，在主语从句中what是主语，所以谓语动词用单数。