The most valid response to the principal's conclusion is:
Yes, because every student had an equal chance to be part of the sample. The sample size also appears to be large enough.
This option reflects the principles of random sampling, where every student had an equal opportunity to be selected, which helps ensure that the sample is representative of the larger population. Even though the principal must ensure that the sample accurately includes students who participate in activities, 200 students is generally a sufficiently large sample size for statistical inference in most contexts.