According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?

(A) Nuclear fusion occurring in the core of the protosun produced energy that heated the nebula. (B) As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy. (C) Radiation from other nearby stars that had formed earlier heated the nebula. (D) The shock wave from a nearby supernova heated the gas. (E) Collisions among planetesimals generated friction and heat.

(B) As the cloud shrank, its gravitational potential energy was converted to kinetic energy and then into thermal energy.

Explanation:

From the theory of the formation of the solar system, the solar nebula which is a massive interstellar cloud flattened into a disk shape as it collapsed due to the gravitational potential energy which was converted to kinetic energy and ultimately thermal energy. This then allowed nuclear fusion to occur and a protosun was formed at the core of the nebula.

Initially, the particles that constitutes the solar nebula were moving randomly in an uncordinated fashion. As the gravitational pull reoriented the particles into a more coordinated pattern. The pull contracted the vast nebula into a smaller size and this was furnished with a kinetic energy. This energy resulted into the heating of the nebula and the centre became very hot. The gravitational pull caused an inward pull on the particles while the pressure of the condensed nebula resulted in an outward pull.