For a number to be divisible by 4, the number formed by the last two digits of that number must be divisible by 4.For a number to be divisible by 9, the sum of its digits must be divisible by 9.Among the choices, choices (a) and (b) are divisible by 4 but of the first two choices, only choice (b) is divisible by 9.Hence choice (b) is divisible by both 4 and 9.