Low-Mass Stars Can Ascend the H-R Diagram in Two Evolutionary

Multiple Choice

Low-mass stars can ascend the H-R diagram in two evolutionary phases called giant phases. What is the difference between them?

A) In the first, the primary production of energy is from hydrogen burning in the core. In the second, the primary production of energy is from helium burning in the core.
B) In the first, the primary production of energy is from hydrogen burning in a shell around the core. In the second, the primary production of energy is from helium burning in a shell around the core.
C) In the first, the star's track on the Hertzsprung-Russell diagram lies along the red-giant branch. In the second, the track lies along the horizontal branch.
D) During the first red-giant phase, the star moves up and to the right along the red-giant branch. During the second red-giant phase the star's track is down and to the left along the same red-giant branch.