Ascientist plans to find out if dams harm a river ecosystem. he interviews 500 enviormentalists and 450 of them believe dams are harmful to the ecosystem. the scientists concludethat 90 percent of people believe that dams are harmful. why is the scientist's comclusion most likely unrealible.

The answer is: the source of information could be biased

The scientist is interviewing environmentalists and then generalized their opinion as "people". An environmentalist is a person that cares about the environment, so they will more likely to deny the option that harms the environment. If the dam harmful to the environment, most environmentalists will not approve it.

the answer to your question is:

c. complementary base-pairing