How did planets and other objects in the solar system form?
A. After the Sun formed, it threw off hot pieces that spun and cooled.
B. The Sun captured objects that formed in other places in the galaxy.
C. Two stars collided, and the broken pieces went into orbit around the Sun.
D. Material in a disc formed large clumps as the Sun fanned in the centre of the disc.

Hint:Learn about solar nebulae and the hypothesis about the forming of the sun and the planets from it. Solar nebula is a gaseous cloud from which the whole solar system was formed by the process of condensation of matter.

Complete answer:
We know that all the planets in our existing solar system are believed to be formed by the spinning disc of dust which formed the Sun. This disc is called the solar nebula and was made mainly of the molecules of hydrogen and helium, but it has also had other elements in lesser proportions.

The nebula was rotating with a certain number of angular momentum around the forming Sun. The particles in the rotating disc started to get together and clump as gravitational force attracted them to each other.

Hence, option D is the correct answer.

Note: There are several theories about the forming of planets and the astronomical objects in the solar system. In between these hypotheses the hypothesis of the solar nebula is accepted widely as it explains all the events in the best scientific way possible. There is a hypothesis called the collision theory which contradicts this solar nebula hypothesis but cannot explain the origin of the solar system like the solar nebula hypothesis.