Answer: c
Step-by-step explanation:
First calculate gravitational force between objects
a) Fg=γ*m1m2/r²
m1=m2=10kg
r=4m
Fg=γ* 100kg²/16m²
Fg=6.25γ
b)Fg=γ*m1m2/r²
m1=m2=5kg
r=4m
Fg=γ*25m²/16m²
Fg=γ*1.56
c)m1=m2=10kg
r=2m
Fg=γ100kg²/4m²
Fg=γ25
d)m1=m2=5kg
r=2m
Fg= γ25kg²/4kg
Fg=γ6.25