Final answer:
The correct answer is stratified sampling. Stratified sampling involves dividing the population into distinct groups, called strata, based on certain characteristics.
Step-by-step explanation:
The correct answer is B. stratified sampling.
Stratified sampling involves dividing the population into distinct groups, called strata, based on certain characteristics. In this case, the classes are the strata, and every student in each class is included in the survey. By including every student in each class, the sample is representative of the entire population of students. This method ensures that each class is proportionately represented in the survey results.
For example, if there are 100 classes and each class has 20 students, the total population is 2000 students. Randomly choosing 5 out of 100 classes and including every student in each class means that the sample size is 5 classes x 20 students = 100 students. This sample is stratified because the classes are the distinct groups (strata) from which the sample is selected.