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.
When comparing the GDPs, Instead of saying compared it to, you might want to type, "in comparison." A few transition words also might help the piece become a bit smoother. Other than that, good job on the writing! It seems very well researched!
Answer:
To release energy slowly in a step by step process.
