Question

what does the h - r diagram show?
the location of planets in the solar system
the relationship between a stars brightness and temperature
the phases of the moon
the distance between stars

Explanation:

The Hertzsprung - Russell (H - R) Diagram is a graphical tool in astronomy that plots stars based on their brightness (luminosity) and temperature. It helps in classifying stars and understanding their life - cycles.

Answer:

The relationship between a star's brightness and temperature