From which of the following do spiral galaxies form?
a. rapidly cooling protogalactic clouds
high-density protogalactic clouds
rapidly spinning protogalactic clouds
colliding/merging protogalactic clouds

The correct answer to the question that is stated above is the third option which is: rapidly spinning protogalactic clouds 

One example of a spiral galaxy is the Milky Way. Spiral galaxies came from a rapidly spinning protogalactic clouds. Spiral galaxies form from the collapse of a protogalactic cloud.