Answer:
(D) 72
Explanation:
A factor is an integer that divides into a whole number without a remainder.
In this case, both 4 and 9 need to be the result of a division of 72 by some number. 4 is a factor of 8, since 8 divided by 2 is 4, but 9 isn't. 9 is a factor of 18, but 4 isn't. Neither 4 nor 9 is a factor of 49. If you divide 72 by 18, you get 4. If you divide 72 by 8, you get 9.
4 and 9 are factors of 72.