In a large city school system with 32 elementary schools (grades 1-5), the school board is considering the adoption of a new policy that would require elementary students to pass a test in order to be promoted to the next grade. The PTA wants to find out whether parents agree with this plan. In each grade level (grades 1 to 5) select 50 students and send their parents a survey. Follow up with a home visit if they do not return the survey within a week. Indicate the type of sampling strategy involved. 0 This sampling strategy is SRS. O This sampling strategy is systematic sampling. 0 This sampling strategy is clustered sampling. This sampling strategy is stratified sampling. O This sampling strategy is convenience sampling