Answer:
C
Explanation:
Randomly surveying 6th graders in the school cafeteria would give jacob valid results because A wouldn't be reliable, because he just wants 6th graders, and B and D would be selective as it would be inside a football store, implying that most 6th graders in there would be tending towards football, and D would be inside a tennis shop, which would imply that most 6th graders there would prefer football. Therefore, the cafeteria would yield the most reliable results.