What Is One Reason Why Convenience Sampling Is Sometimes Seen

What is one reason why convenience sampling is sometimes seen as an inferior approach to sampling?

A) It often produces a sample that is too small.
B) It often produces a sample that is too large.
C) It tends to produce samples that are too homogeneous; the people in the sample are too similar to each other.
D) It tends to produce samples that are too heterogeneous; the people in the sample are too different from each other.