Answer:
The correct answer is: Cluster.
Step-by-step explanation:
Cluster sampling or a Cluster Sample is a method of sampling in research where the investigator divides the participants of his/her study into different groups.
These groups are known as clusters.
The analyses conducted by the researchers come from using participants picked randomly from the clusters.
In this particular case, Angelika wants to study how sixth graders perform in math exams. She obtains a list of all the districts in the state, randomly selects 5 percent of the districts, and administers achievement tests to all sixth graders in these districts. The sampling method used by Angelika is called Cluster sampling.