In which situation would the map key be most useful? to find the distance between chicago and detroit. you need to find countries on a map with oil deposits. you need to determine the date of the map

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