[单选题]
The gravitational atttoof k 8zi: ld4.sx+g4 1r1j agmmy9,gractiv08zki o1 8ddx*./xd8 mx pl;fjoi ifm;e force between two masses is F. If the masses are moved to half of their initial distance, wha8lj x.zdd;k 180idixx /m8f o;fompi*t is the gravitational attractive force?
