Two planets have the same average density but their radii are `R_(1)` and `R_(2)`. If acceleration due to gravity on these planets be `g_(1)` and `g_(2)` respectively, then
A. `g_(1)/g_(2)=R_(1)/R_(2)`
B. `g_(1)/g_(2)=R_(2)/R_(1)`
C. `g_(1)/g_(2)=R_(1)^(2)/R_(2)^(2)`
D. `g_(1)/g_(2)=R_(1)^(3)/R_(2)^(3)`
