Answer:
D is the answer of the question
(2/5) of (2/3) of students = 4/15 of students study French. Then 1-(4/15) = 11/15 of students do not study French. The ratio you want is
(4/15):(11/15) = 4:11
_____
In a math expression "of" means "times".
By multiplication, 12*(1/4) = 3
by division, 12/4 = 3
in words, a quarter of 12 is 3