Scenario D: The administration of a high school wants to know whether students prefer regular or block schedules. They randomly select 30 students to survey from each grade. This is an example of .

The students are first divided into groups based on grade, and then 30 students are randomly selected from each grade. These groups are called strata, so this is stratified random sampling. Simple random sampling would select students randomly from the whole school without ensuring representation from every grade.

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