Use the Following to Answer Questions

Multiple Choice

Use the following to answer questions :
A gene family has been accumulating nucleotide substitutions at a rate of 0.25 substitutions per million years.On average,there have been 80 substitutions between the common ancestor of this gene family and each of the various living forms of this gene.
-Based on these figures,this gene family likely originated _______ million years ago.

A) 20
B) 80
C) 160
D) 200
E) 320