a new house is impossible for the young couple because they haven't saved enough money．
A. Buy
B. Buying
C. Bought
D. Having bought
网友回答
A. Buy
(答案→)B. Buying
C. Bought
D. Having bought
解析：句意：对年轻的夫妇来说买一个新房子是不可能的，因为他们没有攒够足够的钱。这里的is impossible是谓语，前面的内容是主语，用动名词做主语，所以选B。