All Extant Copies of a Gene Eventually Coalesce; This Occurs

Multiple Choice

All extant copies of a gene eventually coalesce; this occurs because

A) a particular allele becomes fixed in the population.
B) all extant genes coalesce at the same time in the same individuals.
C) the rate of coalescence speeds up as a population increases in size.
D) the original population consisted of only a single individual with the ancestral allele.