Question

what does it mean when a star moves off the main sequence on the h - r diagram?
it has run out of hydrogen fuel
it is just beginning to form
it is getting hotter and brighter
it is turning into a planet

Explanation:

On the Hertzsprung - Russell (H - R) Diagram, stars spend most of their lives on the main sequence fusing hydrogen into helium in their cores. When a star runs out of hydrogen fuel in its core, it can no longer maintain the equilibrium that keeps it on the main sequence and moves off of it.

Answer:

It has run out of hydrogen fuel