Gravity causes objects to be attracted to one another. This attraction keeps our feet firmly planted on the ground and causes the moon to orbit the earth. The force of gravitational attraction is represented by the equation

F=r2Gm1m2

where F is the magnitude of the gravitational attraction on either body,m1 andm2 are the masses of the bodies, r is the distance between them, and G is the gravitational constant. In SI units, the units of force are kgm/s2, the units of mass are kg, and the units of distance are m. For this equation to have consistent units, the units of G must be which of the following?

a.ms2kg3

b.m3kgs2

c.kgs2m3

d.kgs2m