are 因为当population被分数或百分数来修饰时谓语用复数。 这个答案一定是对的。
is主语是population,污染,不可数名词
is。
给你个权威例句:
The IMF estimates government wages account for 12 percent of GDP, but 63 percent of the population remains undernourished.
来源:
http://www.msnbc.msn.com/id/37603745/ns/business-forbes_com/
填is, percent of + n, 动词形式由前面的n决定
is,主语是population