During the First One-Ten-Thousandth Second (10^-4 S) of the Life

Multiple Choice

During the first one-ten-thousandth second (10^-4 s) of the life of the universe, antiprotons were very common. For every billion antiprotons, how many protons were there?

A) an unknown number, because the early universe was opaque and we cannot see what conditions were like then
B) 1 billion and 1, thus producing the matter we see today
C) 10 billion, thus producing the dark matter we see today
D) exactly 1 billion, because protons and antiprotons were created in equal numbers