Question

question 4
what is the star - gas - star cycle?
the process by which galaxies
ecycle\ gas & dust to form new stars.
the process by which a reflection nebula can emit hydrogen atoms.
the process by which an hii region glows.
the process by which cosmic rays produce all elements heavier than h & he.

Explanation:

The star - gas - star cycle is about the continuous process in galaxies where gas and dust are recycled to form new stars. Reflection nebulae, HII regions, and cosmic - ray element production are different astrophysical processes not related to the star - gas - star cycle.

Answer:

The process by which galaxies "recycle" gas & dust to form new stars.