The mass of the moon is 1/81 of the mass of the earth. Compa…

The mass of the moon is 1/81 of the mass of the earth. Compared to the gravitational force that the earth exerts on the moon, the gravitational force that the moon exerts on the earth is: A. 812 = 6561 times greater. B. 81 times greater. C. equally strong. D. 1/81 as great.