Imagine a Genomic Researcher Who Is Analyzing the Genome of Different

Imagine a genomic researcher who is analyzing the genome of different types of cats. She finds that a particular sequence in the North American Bobcat genome is exactly identical to a sequence found in the common house cat, while most other sequences in those two genomes differ at many nucleotides. (The most recent common ancestor between bobcats and house cats is estimated to be about 6.8 million years, plenty of time for mutation to generate DNA sequence variation.) Which of the following could explain the identical sequence in these otherwise differing genomes?

A) The sequence encodes a gene that is critical for life and cannot be easily mutated while retaining function.
B) The sequence is contained in a retrovirus that has infected both species.
C) The sequence encodes a protein critical for the production of fur color.
D) The sequence is from an intron of a gene that encodes a muscle protein.