--What do you think made Mary so upset ?- her new bicycle.A. As she lostB. LostC. Losin

问题补充：

--What do you think made Mary so upset ?

--- her new bicycle.

A. As she lost

B. Lost

C. Losing

D. Because of losing

答案：

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。