When the Big Bang Began,all the Fundamental Forces Were Unified

When the Big Bang began,all the fundamental forces were unified and behaved like a single force.As the universe expanded and cooled during the Big Bang,when did the strong nuclear force first become a separate force?

A) at the start of quark confinement, when the universe was about 10-⁶ s old
B) when pair production ceased, when the universe was about 1 s old
C) at the Planck time, when the universe was about 10-⁴³ s old
D) at the start of the inflationary period, when the universe was about 10-³⁵ s old