After It Leaves the Main Sequence, a Star of More

After it leaves the main sequence, a star of more than 1 solar mass moves generally to the right on the H-R diagram because the star's

A) surface temperature is increasing while its radius is decreasing.
B) surface temperature is decreasing while its radius is increasing.
C) core is expanding while its outer layers are contracting.
D) core is expanding, causing its outer layers to expand as well.