After the sun leaves the main sequence, its helium core will contract to a few times the size of Earth before helium burning begins. Which of the following statements about what will happen to the sun's outer layers is true? A. The outer layers will contract with the core, leaving the sun about 10 times smaller and a few 100 times less luminous. B. The contracting helium core will heat the surrounding hydrogen-burning shell, causing it to burn hydrogen and produce energy more quickly. This will inflate the outer layers, leaving the sun about the size of Mercury's orbit and a few 100 times more luminous. C. The contracting helium core will heat the surrounding hydrogen-burning shell, causing it to burn hydrogen and produce energy more quickly. This will inflate the outer layers, leaving the sun about the size of Mars's orbit and a few 1000 times more luminous.