Answer :
The goal of our sampling is to determine the favorite sport of the students in the high school. For that we need to sample from all the students in the school, trying to get as diversified as possible. Let's analyze each strategy and choose the better one.
Kenneth goes to a football field, since he's already at an sports event, most of the students going there will have football as their favorite sport, skewing the data towards that. Therefore this is not an effective strategy.
Lynn stands at the entrance of the school sampling 20 students that arrives, this also doesn't take a lot of students into account, because most of the people that arrive early presumably have a simillar personality.
Maleka uses a list of students from the whole scools, then chooses at random the names she'll interview. This seems like a good approach, because it's from the whole school, and there isn't a significant bias inserted into the sampling.
Finally tony samples all the students from his class, this also does not sound like a good strategy, because they don't represent the whole school.
The best strategy is the one used by Maleka, option C.