Aresearcher wants to compare student loan debt for students who attend four-year public universities with those who attend four-year private universities. she plans to take a random sample of 100 recent graduates of public universities and 100 recent graduates of private universities. which type of random sampling is utilized in her study design? choose the correct answer below.

a. a cluster sample because the population is divided into separate groups, or clusters, and all subjects from a randomly selected cluster (or sample of clusters) are selected.

b. a stratified sample because the population is divided into separate groups and each group is randomly sampled.

c. a stratified sample because the population is divided into separate groups.

d. a simple random sample because she randomly samples people from one group.