Please indicate which type of sampling design is most appropriate for each of the following studies. The choices are SRS, stratified random sampling, and matched pair design.

a) A student organization has 55 members at three difference campuses. Out of these members, 2 students are randomly selected at each campus to attend a conference.
b) A course administrator wants to know if there is a difference with how satisfied distance students are with getting their questions answers based on whether they are on campus or not. Therefore, she randomly selects 10 students in the distance section who are not on campus and 10 students in the distance section who are on campus and asks them whether they are satisfied with how their questions are being answered.
c) A pharmaceutical company wants to determine if the size of a new pill is too large to take. They randomly select 200 people and asked if they could swallow the pill or not.
d)Roads form cracks from the top down and the bottom up. A researcher wants to know if the top down cracks are larger than the bottom up cracks.