题目内容：

i don't play football now,but i _____when i was a child.是used to it 还是used to it 还是used to
A used to
B used to it
C used to do

优质解答

used to （i don't play football）定语省略宾语

追问：

可以详细解释一下吗

追答：

我现在不踢球了，虽然我小时候经常踢 i don't play football now, but i used to（which）when i was a child. i used to（which）which指的是i play football 这件事，由于是在长句中做宾语，which可以省略