A survey was conducted among the school children of the Muscat region to determine their mental anxiety due to COVID-19. Five schools were selected randomly from the list of all schools in the region...

Extracted text: A survey was conducted among the school children of the Muscat region to determine their mental anxiety due to COVID-19. Five schools were selected randomly from the list of all schools in the region and all the students of the selected school were interviewed. What type of sampling design was employed? O A. Stratified Sampling O B. Random sampling O C. Systematic Sampling D. Cluster Sampling