Final answer:
The nebular theory states that as the solar nebula collapsed, it got hotter, its rate of rotation increased, and it flattened into a disk.
Step-by-step explanation:
The statement is true. According to the nebular theory, as the solar nebula collapsed due to gravity, it got hotter and its rate of rotation increased. This increase in rotation caused the nebula to flatten into a disk shape. The existence of this disk-shaped rotating nebula explains the primary motions in the solar system, including the formation of planets and their orbits.