A. The last number is 3. B. The sum of the digits of the number is a multiple of 3. C. The first two digits are divisible by 3. D. The number ends in an odd digit.
B is correct. Also, if you have a number such as 876543 and add the digits, it is 33. If you did not know this was divisible by three, you could add 3+3 and get 6, which is divisible by three, making 876543 divisible by three.
