英语单选题，， 解释一下

water pollution; the polluted water
exchange for

第一个是水污染，应该用污染的名词形式。。
第二个是过去分词做形容词，表示被污染的水

had somebody do something
因此要用动词原形。exchange sth for sth.表示用某物交换某物

C. pollution, polluted
第一个pullution是名词,water pollution是水污染的意思,第二个pullted是动词,意思是被污染的水。

B exchange, for
have sb do sth是个固定用法
句子意思是哪个男孩很淘气,他让女孩用玩具换了他的糖

29. People caused a lot of water________, and the ______water did harm to their health.
C. pollution, polluted
1) cause sth.( water pollution)
2) . have sth done.

38. This boy is very clever. He had the girl ________ her toy _____ his candy.
B exchange, for
1) have sb. do sth.
2) exhange sth for sth.

c
pollution是名词,第一空意思为人类制造了大量的水污染
a lot of后肯定要接名词
而polluted为形容词,句中意思为"污染的水有害于人类健康",polluted修饰名词water

b
have sb do sth 是固定搭配,意思是让某人做某事,与let,make用法相同.而exchange for 意为交换

29 C
人们造成了水污染，这里污染用名词pollution
被污染的水伤害人