Answer: B

Since there are 4 numbers in A and 5 numbers in B, the number of possible products is 4x5 = 20. The number of desirable outcomes is the number of pairs that result in a product of 24. Those are: (2,12), (4, 6), and (6, 4), where the number from A is followed by the number from B. That's 3 possibilities.

The probability, then, is 3/20 = 0.15, choice (B).