If a Lecturer Surveyed His Students About Their Attitudes Concerning

If a lecturer surveyed his students about their attitudes concerning the public pension system and concluded that young adults doubt that they will ever receive public pension benefits, his conclusion would be flawed because

A) his students were not a representative sample of young adults.
B) he did not survey the entire population of young adults.
C) he knew his subjects before he surveyed them.
D) his students were a random sample.