The answer is B. 3 : 5 = 12 : 20
2:3 doesn't equal 3:2 because they are backwards
42:7 doesn't equal 6:2 because 42:7 simplifies to 6:1 which is not equal to 6:2
14:6 doesn't equal 28:18 because 14:6 simplifies to 7:3 and 28:18 simplifies to 14:9, and these two proportions are not equal