I got an undergraduate degree in statistics, and what we were taught was that there are lots of valid ways to sample but how you sample affects how you can gene

I got an undergraduate degree in statistics, and what we were taught was that there are lots of valid ways to sample but how you sample affects how you can generalize the results. Since this is a college survey and not an FDA trial, it's probably ok to proceed with D or E in addition to A (B is the only bad answer). That said, there most certainly is a correlation between in non-response and lower scores on the survey, so when presenting findings it's important to represent that concern. In general, surveys are pretty weak means of drawing conclusions, but sometimes it's the means.