Cheryl wants to find the number of hours seventh-graders do homework each week. There are 297 girls and boys in seventh grade. Which is the best way for Cheryl to get a representative sample without spending too much time?

A.) She can survey 15 of her friends in the school.

B.) She can survey every sixth-grade student in the school.

C.) She can randomly survey 50 girls in the entire school.

D.) She can randomly survey 50 seventh-graders in the school.