Answer:
Step-by-step explanation:
The formula is

so anything making m larger increases the force
anything that decreases r makes F smaller.
B
So if you double each of the masses, the force becomes 4 times as large.

C
If the distance r is doubled, the force becomes 1/4 as large. That's because
r becomes 2r and when 2r is squared it becomes 4r^2. But that is in the denominator, so you are dividing by 4.
D
This is the hard one. You really have to understand fractions to know what is happening. it might be easier if we use decimals. Each r become 1/2 r or 0.5r
When you square that, you get 0.25 r^2
Just try it with something simple. Let r = 1 Now suppose that Gm1m2 = 20
20/0.25 = 80
When you 1/2 the distance the force is going to be 4 times as large.