Answer:
Explanation:
The right answer is in the mind of the person asking the question. I think your best answer is 2. The distance the objects are apart and the two masses of the objects.
Why am I hesitant. It is because the marker could be counting the 2 masses separately and the distance squared as 2 more factors. I'm going to stick with 2 but don't be surprised if it turns out to be something else.