Why Does Fusion Take Place at Very High Temperatures

Why does fusion take place at very high temperatures?

A) Gamma rays, a product of fusion reactions, can only exist at very high temperatures.
B) High temperatures and pressures are required to confine the hydrogen plasma so that fusion can take place.
C) High temperatures mean high collisional velocities, which can allow protons to overcome their mutual electrical repulsion.
D) High temperatures produce bluer, more energetic photons that are required to initiate the fusion reaction sequence.