Q:Rob is an amateur astronomer. Recently, he detected four asteroids, asteroid A, asteroid B, asteroid C, and asteroid D. Asteroid A and asteroid B are of the same mass, but asteroid A is farther from the earth than asteroid B. Asteroid C and asteroid D are at the same distance form the earth, but asteroid C has more mass than asteroid D. He also figured out that all of these asteroids have less mass than earth.  In clssical theory, if Rob needs to find out the object with stronger gravitational pull, which one would he choose, earth or asteroid A?
A: