Critical Reasoning

From 1970 to 1990, sea otters made up a steadily decreasing percentage of the marine life population in North America. The increasingly widespread effects of pollution and habitat destruction were responsible for this decrease. However, although pollution was a more frequent target of environmental legislation, it was found that pollution in North America increased by a greater percentage than did the rate of habitat destruction.

Which of the following, if true, most helps to account for the finding?
(A) Environmental legislation limiting industrial pollution was much more financial onerous on North American firms than legislation protecting marine habitats.
(B) The decreasing percentage of sea otters among the marine population had a positive effect on the species that sea otters typically prey on.
(C) Most of the habitats likely to be destroyed by human activity had already been compromised for marine life by 1970.
(D) Habitat destruction was a more frequent target of environmental legislation than pollution in the decade preceding 1960.
(E) Marine life as a whole was more significantly affected by pollution than by habitat destruction.

[spoiler]OA: C[/spoiler]