A. 1 : 6 = 20 : 120 = 5 : 30
1*20 : 6*20 = 20 : 120
1*5 : 6 * 5 = 5 : 30
So they are equivalent ratios
B. 1 : 6 = 4 : 18 = 6 : 36
1*4 : 6*4 = 4 : 24 which is not equivalent to 4 : 18
so, they are not equivalent ratios
C. 1 : 8 = 20 : 120 = 3 : 24
1*20 : 8*20 = 20 : 160 which is not equivalent to 20 : 120
so, they are not equivalent ratios
D. 1 : 8 = 3 : 32 = 5 : 48
1*3 : 8*3 = 3 : 24 which is not equivalent to 3 : 32
so, they are not equivalent ratios