Narrowed it down to A and C.

Hi, we are trying to prove the argument that the real motive is profit, not concern for otters. The environmentalists argument is flawed because he treats this as an either or situation, when it is possible that both motives play a part. A eliminates that possibility, thus proving their argument. C does not prove the argument. Past behavior does not guarantee future behavior, and showing a high regard for profit is not mutually exclusive with also caring about otters.