exchange
1.可以说They（指两个人）exchanged caps（他们俩交换帽子），也可以说They exchanged gifts（或compliments, glances, smiles等）。对于行动，有时用单数形式。例如：They exchanged a compliment（或a glance，或a smile）.
2.in exchange for用在give和get或receive后面都可以。例如：I should like to give my pen in exchange for yours. 和I should like to get（或receive）your pen in exchange for mine.
3.mutual exchange, exchange mutually, exchange with each other（或one another）和exchange together该避免，单用exchange够了。
