Answer:
B) Cluster Sampling.
Step-by-step explanation:
Cluster sampling refers to a methodology for probability sampling, in which researchers split the populace into several study groups or one can say clusters. And after this investigators pick random groups for collecting and analyzing data, using a systematic random or simple random sampling technique, depending on the research subject. As per the question, instead of 200 grids selected a cluster of 30 grids for the research and therefore it is a classic of cluster sampling.