The compact concentration of most asteroids in a well defined belt suggests one of two possible origins: either the fragments of a planet broken up long ago, or they are primal rocks that somehow never managed to form a genuine planet. On the basis of the best evidence currently available, and consistent with current theories of solar system formation, researchers strongly favor the latter view

Question

There is far too little mass in the belt to constitute a planet, and the marked chemical differences between individual asteroids indicate that they could not all have originated in a single planet. Instead, astronomers believe that the strong gravitational field of Jupiter continuously disturbs the motion of these chunks of primitive matter, nudging and pulling at them, preventing them from aggregating into a planet.

a. Modern astronomers believe that asteroids are rocks that are fragments of a planet that has broken up many years ago.
b. Asteroids differ markedly in chemical composition, making them difficult to understand.
c. Asteroids may have formed together as a planet except for the gravitational pull of the Earth.
d. Asteroids are compact and travel in a well defined belt, suggesting that they are fragments of a long ago planet or that they are primal rocks that have not formed into a planet.

Answer 1

d