Before I answer this question, tell me first what is your opinion regarding this?
You are doing research on hospital personnel--orderlies, technicians, nurses, and doctors. You want to be sure you draw a sample that has cases in each of the personnel categories.
Refer to Research Scenario. You want to use probability sampling. An appropriate strategy would be
a. simple random sampling
b. cluster sampling
c. stratified sampling
What do you think?
Simple random sampling is used when the population is NOT divided into any groups or when the required sample does not have any group-restriction. But here your population consists of 4 groups (orderlies, technicians, nurses and doctors) and you want the required sample to cover ALL the 4 groups. So it is not Simple random sampling.
Cluster sampling means your population is divided into some groups and SOME (not all) of the 4 groups are chosen and all the population members in those selected groups are considered. So here you CAN NOT get all the 4 groups in your sample.
Stratified sampling means a sample from EACH of the groups in the population are drawn, thus you get 4 samples from 4 groups, which is exactly what you want.
So it is C.