You've been asked to determine the percentage of students who would support gay marriage. You want to take a random sample of fellow students to make the estimate. Explain whether each of the following scenarios describes a random sample.
a. You ask all students eating lunch in the cafeteria on a Tuesday at 12:30 p.m.
b. You ask every 10th student from the list of enrolled students.
c. You ask every 10th student passing by the student union.
d. What sampling procedure would you recommend to complete your study?