Answer:
a) cluster sampling
Step-by-step explanation:
In cluster sampling method, each member of a population is assigned to one and only one group.This means clusters are formed through probability method usually a simple random sampling.The participants in the clusters are the only one to be surveyed.
In this example, simple random sampling is used to identify 12 home rooms(cluster) where a group of 20 students (participants) in each room is given the survey.
pi·(7.2/2)^2·x = 2·pi·(7.2/2)^2 + 2·pi·(7.2/2)·x
x = 4.5 = 4 1/2
O = V = 1458/25·pi = 58.32·pi
