The Crossover Point from Radiation to Matter Domination Occurred:
A)when $16,000 \mathrm {~K}.$

The crossover point from radiation to matter domination occurred:

A) when the strong force separated from the other two forces.
B) with the emission of the cosmic background radiation.
C) about 50,000 years after the Big Bang, at a temperature of about $16,000 \mathrm {~K}.$
D) with the creation of neutrons and protons, at about $10^{13} \mathrm {~K}$
E) with the creation of electrons and positrons at about $6 \times 10 ^ { 9 } \mathrm {~K}$