Select all the correct answers. Events involving a disk-shaped nebula occurred before the nuclear fusion that led to the birth of the solar system. Which two statements about the disk-shaped nebula are true?
A Gravity caused the disk-shaped nebula to shrink.
b Gravity caused the nebula to flatten out in its disk-like shape.
c Rotational motion caused the disk-shaped nebula to shrink.
d Rotational motion caused the nebula to flatten out in its disk-like shape.
e The flattening of the disk caused the speed of rotation to decrease.