You are interested in the experiences of women in science, technology, engineering, and mathematics (STEM) majors. First, you make a list of all universities in Michigan. Then you randomly select 3 of those universities. Following this selection, you collect data from all female STEM majors within these three universities. This is an example of:

a. Biased sampling
b. Simple random sampling
c. Multistage Cluster sampling
d. Cluster sampling
e. Stratified sampling