What is the average time it takes to transport a wounded soldier back to the United States? Why does it take longer to get a soldier home than it would to just fly to a war zone in a plane?

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