Genes from Many Isolates of the Influenza Virus Have Been

Genes from many isolates of the influenza virus have been sequenced. In certain regions of the genome, nonsynonymous substitutions occur much more frequently than do synonymous substitutions. What can we infer from this pattern?

A) A great deal of genetic drift is taking place.
B) Most of the amino acid changes are neutral.
C) Strong stabilizing selection is acting on this gene.
D) Strong selection for change is acting on this gene.
E) Mutations that change the amino acid are ­disadvantageous.