Answer :
Using sampling concepts, it is found that the correct option is:
A.) cluster sampling
Samples may be classified as:
- Convenient: Drawn from a conveniently available pool.
- Random: All the options into a hat and drawn some of them.
- Systematic: Every kth element is taken.
- Cluster: Divides population into groups, called clusters, and each element in the cluster is surveyed.
- Stratified: Also divides the population into groups. However, only some elements of each group are surveyed.
In this problem:
- The students are divided into groups, according to their periods.
- All the elements of a period are selected, hence, cluster sampling is used, and option A is correct.
To learn more about sampling concepts, you can take a look at https://brainly.com/question/25122507