At Lincoln Elementary School, 4/5 of the students buy lunch at school. Of those students, 1/3 buy milk with their lunch. What equation can be used to find what fraction of the students buy milk?

A. 1/3 ÷ 4/5

B. 1/3 - 4/5

C. 1/3 + 4/5

D. 1/3 x 4/5