C because a market research helps when you are buying something which he is (car) and this is a secondary resource because it is recommended by someone rather than them finding the research himself.
The correct answer is B indeed. It is an example of plain folks because the speaker appeals to the citizens of his town, and to the knowledge that he shares with the other members of the community. This strategy is quite basic, as shown by this example, because the author makes a claim that most people would agree with, without actually providing evidence or a series of logical arguments.
Apparently this included "inappropriate." words or phrases, so I took screenshots of what I had typed, hope it helps.
5. its- possessive
6. he- subject
7. me- subject
8. their- possessive
