Which of the following is a proportion?
A.3/4 = 12/15
B.8/10 = 6/8
C.6/9 = 8/12
D.4/6 = 9/12
A.3/4 = 12/15
B.8/10 = 6/8
C.6/9 = 8/12
D.4/6 = 9/12