Please help me these questions. I just need ABC (but if it is feasible, plz give me "short" calculations) Please do it as carefully as possibleThanks so much!

6. Every seventh customer entering a mall is asked to select his or her favorite store. This is an example of this kind of sampling: A: Random B. Cluster C. Systematic 7. Nursing supervisors are selected using random numbers to determine annul salaries. This is an example of this kind of sampling: A: Simple Random B. Cluster C. Systematic 8. Mail carriers of a large city are divided into four groups according to gender (male or female) and according to whether they walk or ride on their routes. Then 10 are randomly selected from each group to determine whether they have been bitten by a dog in the last year. This is an example of this kind of sampling: A: Random B. Cluster C. Stratified 9. In a large school district, all teachers from two buildings are interviewed to determine whether they believe the students have less homework to do now than in previous years. This is an example of this kind of sampling: I A: Random B. Cluster C. Stratified