Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
A) surface temperature on the horizontal axis and luminosity on the vertical axis
B) mass on the horizontal axis and luminosity on the vertical axis
C) surface temperature on the horizontal axis and radius on the vertical axis
D) mass on the horizontal axis and stellar age on the vertical axis
E) interior temperature on the horizontal axis and mass on the vertical axis
Answer: A