34. effects of chronic use include lung cancer, memory impairment, decreased blood flow to the brain, and reduced oxygen availability in all regions of the body. a. heroin b. cocaine c. marijuana d. alcohol

Donald is studying the eating habits of all students attending his school. he samples the population by dividing the students into groups by grade level and randomly selecting a proportionate number of students from each group. he then collects data from the sample. which type of sampling is used? select the correct answer below: systematic sampling convenience sampling stratified sampling cluster sampling