Answer:
The correct answer is D. I and II only
Explanation:
Using the following formula to verify all possible options:

Checking for 15.15:
Quotient = 15

Completely divisible, this means that this option is Correct.
Checking for 18.16:
Quotient = 18

Completely divisible, this means that this option is Correct.
Checking for 17.17:
Quotient = 17

Not completely divisible, so this is the wrong choice.