(A) is the correct answer. In a chess board, there are 64 squares of which 32 are white and 32 are black. Since 2 of one colour and 1 of other can be 2W, 1B, or 1W, 2B, the number of ways is (32C2 × 32C1) × 2 and also, the number of ways of choosing any 3 boxes is 64C3.
Hence, the required probability