Answer:
1. Gravity caused the disk-shaped nebula to shrink.
Rotational motion caused the nebula to flatten out in its disk-like shape
2. Comet - has a characteristic glow
Meteoroid - usually burns up if it enters Earth's atmosphere
Gas giant - primarily made of hydrogen and helium
Asteroid - varies greatly in size from one to the next
3. They are made of denser objects, which can condense at relatively high temperatures
They are made of heavier elements, which have a stronger gravitational attraction to the Sun
Explanation:
These should be the correct answers. Hope this helped!