The Best Explanation for the Phenotypic Differences Between Humans and Chimps

Multiple Choice

The best explanation for the phenotypic differences between humans and chimps despite the great similarities in their gene-coding sequences is

A) the vast differences in exons between their genomes.
B) the vast differences in the introns between their genomes.
C) the "junk" DNA of humans contains important sequences not present in chimps.
D) differences in gene expression between species.