Carbon Fusion in Massive Stars Combines Helium and Carbon to Produce

Carbon fusion in massive stars combines helium and carbon to produce oxygen.Carbon fusion is followed by oxygen fusion in which oxygen is burned to produce sulfur.Why is a higher temperature required for oxygen fusion than for carbon fusion?

A) Because of extensive mass loss between the carbon-fusion and oxygen-fusion stages, higher temperatures are required for nuclear reactions in the relatively rarified stars in which oxygen fusion takes place.
B) Larger nuclei, like oxygen, have more protons and are therefore repelled more strongly from other nuclei. Thus, faster speeds (at higher temperatures) are required to bring these nuclei together than are required for smaller nuclei.
C) Free neutrons are required in greater numbers to enable the oxygen reaction, and higher temperatures are required to produce them.
D) The enormous neutrino flux in the core of a massive star inhibits nuclear reactions. High temperatures are necessary to force these neutrinos out of the star so nuclear reactions can proceed.