The administration at a local high school is considering building a new gym. In order to find out how the student body feels about this, a student organization decides to conduct a survey of the students. Which of the sampling methods in A–D is a simple random sample from all the students at the school? 

A. Survey random students who are leaving after school sports practices. 

B. Randomly select 40 students in each grade level and survey the selected students. 

C. Randomly select two homeroom classes from the 50 homeroom classes at the school and survey all students from those two classes. 

D. Obtain a list of all students attending the high school, randomly select students from the list, and survey the students selected.