Helium Fusion Requires a Higher Temperature Than Hydrogen Fusion Because

Helium fusion requires a higher temperature than hydrogen fusion because ____.

A) helium has to be driven into the outer layers of a star for fusion to occur
B) helium bonds with carbon at the temperature of hydrogen fusion
C) the repulsion between two helium nuclei is much greater
D) hydrogen must be driven off so it doesn't interfere with the helium nuclei