Answer: C. The company might fear that the letter-writing campaign will become a boycott if it doesn't respond.
Step-by-step explanation:
A letter-writing campaign might be a precursor to larger things such as a boycott and this is alone to ensure that companies pay attention to the concerns of those writing the letters.
The logic is simple. If the organizers of the people writing the letters could organize so many people to write letters, they could just as well organize these people to boycott the company if they do not get their way and this would be harmful to the business.