Nayara wants to know the percentage of each grade level of students at her school who drive to school. She has 4 grade levels in her school.Which of the following survey methods will allow Nayara to make a valid conclusion about what percentage of each grade level of students drive to school?

Choose 1 answer:
a. Randomly select 48 students who drive to school and ask them their grade level.

b. Randomly select 12 students from each grade level and ask whether they drive to school.