Which table shows a proportional relationship between x and y?

x 1 2 3 4
y 4 10 12 16

x 2.5 3 5 6
y 5 6 10 15

x 1 3 4 7
y 2 5 8 14

x 7 14 28 35
y 1 2 4 5

There are 18 female students and 16 male students in a class. which of the following expresses the ratio of female students to male students in simplest form? а) 10 b) 9 to 8 c) 8: 9 d)18/16