问题补充：
Your pocket money can be used to charity, but you used to a lot on snacks.
A. supporting, spend
B. support, spending
C. support, spend
D. supporting, spending
答案：
A. supporting, spend
B. support, spending
(答案→)C. support, spend
D. supporting, spending
解析：be used to do sth，被用来做某事，used to do sth，表示过去常常做某事，故选C
