Answer:
C.
Explanation:
The result of the multiplication must end in 0 so A, D nor E are the answer.
Consider B:
34 * 45
Neither of the numbers are divisible by 7 so it's not this one.
It's C because:
56 is divisible by 1, 2,4,7,8 and
45 is divisible by 3, 5, 9
The factors contain 2 and 3 so its also divisible by 2*3 = 6.
The product ends in 0 so its also divisible by 10.