Methods used to reduce sulfur dioxide emissions from smokestacks are an attempt by humans to

A lessen the amount of insecticides in the environment

B eliminate diversity in wildlife

C lessen the environmental impact of acid rain

D use non chemical controls on pests

The answer is (c) lessen the environmental impact of acid rain. This is because acid rain is mainly due to the sulfur dioxide (and nitrogen oxides) emissions from smokestacks (and motor vehicles). Controlling the sulfur dioxide emissions would mean an attempt to lessen the environmental impact of acid rain.