What should be included in your first draft?
a. the revised introduction and conclusion
b. the details of research you've done
c. the main idea and general support of the idea
d. the changes from proofreading and editing

The question is asking us what should be included in your first draft. The first draft is not yet a finished work, it should not include the details and it is expected that it would undergo a lot of changes after that. Therefore, it should just include the main outline and the main ideas of the work, so the correct answer is C. The main idea and general support of the idea