Carlos Runs a Study Where He Wants to Compare Blind

Carlos runs a study where he wants to compare blind and deaf college students and their perceptions of professor sensitivity to the needs of other-impaired students. To conduct his study, he contacts organizations consisting of blind and deaf college student groups at universities across the country. He then randomly selects members from each organization for participation in his study. What form of probability sampling did he use?

A) simple random sample
B) stratified random sample
C) cluster sample
D) systematic sample