国际盲人读物可以免收水陆路邮费、挂号费、（）
A、航空运费
B、SAL费
C、回执费
D、撤回或修改更正收件人姓名地址申请费
参考答案：C, D
— What great trouble I have solving this problem now！
—_____ my advice, you ________less trouble.
A．If you had taken, would have had
B．If you took, would have
C．If you had taken, would have
D．If you take, will have
下图是突触模式图。请据图回答：（[]内填序号）
突触由[]（）、（）、[]（）三部分构成。
