I want to post this to a friend in America.will he have to pay duty____ it?

问题描述:

I want to post this to a friend in America.will he have to pay duty____ it?
A from
B with
C for
D on
这里的最后的那个it 是代替什么?
为什么要使用on?

duty on it ====关税
固定短语
加分吧 ----heihei