A teacher has 36 students who were randomly assigned to 6 rows of 6 desks. She wants to survey the students about the homework policy. Which of the following uses cluster sampling?
Roll a fair number cube. Use the number rolled to pick a row of students. Survey every student in that row.
List the students according to their grade in the class. Survey one A student, one B student, etc.
For each row, flip a coin. If it is heads, survey all the boys in that row. If it is tails, survey all the girls in that row.
Select a student by rolling a fair number cube twice. The first roll gives the row number, and the second roll gives
the seat number. Then repeat.