Professor Kramer Has Decided to Measure How Happy His Students

Professor Kramer has decided to measure how happy his students are with his teaching this semester.He is teaching two classes this semester-Psychology and Law and Introduction to Neuroscience.He gives his students a survey.

-In the above scenario,Dr.Kramer plans to give his survey only to his Psychology and Law students because he sees them on Mondays,Wednesdays,and Fridays and he can spare the class time (unlike in his Introduction to Neuroscience class,which only meets on Tuesdays and Thursdays) .Which of the following is true?

A) This will lead to a biased sample because the type of students who take Psychology and Law may be different from the type of students who take Introduction to Neuroscience.
B) This will lead to a biased sample because of self-selection.
C) This will lead to a biased sample because the Psychology and Law students have a lot of time to complete the survey.
D) The will lead to a sample that is representative of both of his classes.