Answer choice C supports the conclusion that some advertisers are motivated by moral as well as financial considerations. Taking answer choice C as true (as we are supposed to in Strengthen questions), we see that the advertiser would stand to gain financially if they left their ads in the publication. However, they did not choose to keep their ads in this publication, meaning that there must have been some other consideration playing a role in their decision. Namely, their moral disapproval of such publications.
They would, in this case, rather take the financial loss but maintain their morality than appear in this publication.