We live in a small flat but last year we bought a house.
A. would
B. had to
C. used to
D. ought to
网友回答
A. would
B. had to
(答案→)C. used to
D. ought to
解析：考查情态动词：A. would过去常常，B. had to 不得不，C. used to 过去常常，（现在不这样）D. ought to应该，句意是：我们过去住在小公寓，但现在我们买了大房子。选C。