List all the schools in the school district. For each school, list all the teachers at the school; sort them alphabetically within each school. For each school, list the weights of the students of the teacher who is first on that school's sorted teacher list. Combine the lists and average the results. a. a simple random sample
b. a systematic random sample
c. a stratified random sample
d. a random cluster sample
e. a random stratified cluster sample
f. a multistage random sample
g. a multistage random cluster sample
h. a random stratified multistage cluster sample
i. a systematic sample