Which change will always result in an increase in gravitational force between two objects

Hello, the gravitational force has the form , where M1 and M2 are the masses of the objects, G is a constant and r is the distance between the two objects.

first: increasing the mass of the objects, the masses are in the numerator, then if whe increase either M1 or M2 (or both of them) then the gravitational force will increase.

second: decreasing the distance between the objects ( r in this case). r is in the denominator, si if r is smaller, the result of the division will be bigger, so if r decrease, then the gravitational force increase.

i think the answer is a, hope this : )