A homework question in someone’s 11th grade statistics class
The answer has to be A, under reasonable assumptions.  If you assume that the university wants to find out the opinions of all students, and if you assume that students who didn't respond still have opinions, then the problem is that the students who didn't respond may have different opinions from the students who did, skewing the results.  Only choice A tries to solve this problem.<p>People here are drastically overthinking it.  Yes, it's true that the problem didn't <i>state</i> those assumptions, but you are supposed to make them, not to say "the university didn't give us its criteria for 'best plan' so all the answers are equally good".  Given the way that problems like this work, it's obviously meant to test knowledge of the specific idea that the people who respond may be nonrepresentative of all the opinions.  Only response A shows knowledge of this idea.