--What do you think made Mary so upset ?
--- her new bicycle.
A. As she lost
B. Lost
C. Losing
D. Because of losing
网友回答
A. As she lost
B. Lost
(答案→)C. Losing
D. Because of losing
解析：考查动名词做主语。动名词做主语表示经常性习惯性的行为。句意：—你认为什么让Mary如此难受？—丢了新的自行车。答句是为了回答what。四个选项中只有C项可以做主语。故C正确。