1．He gave her French lessons in e________ for her teaching him Chinese.
答案：exchange
2．They are different from each other in hobbies and ________ (娱乐)．
答案：entertainment
3．There is no living thing in the river because it is seriously p________.
答案：polluted
4．Your room is s________ to mine, so they have much in common.
答案：similar
5．The street was c________ with people and the traffic was held up.
答案：crowded
