A Gene Has Been Discovered in the Genome of a Eukaryote

A gene has been discovered in the genome of a eukaryote that is identical to a gene of a bacterium that the eukaryote normally engulfs and digests. This is probably due to

A) a mutation of an existing gene in the eukaryote that coindcidentally is the same as the bacterial gene.
B) horizontal evolution.
C) horizontal gene transfer.
D) a mutation of an existing gene in the eukaryote that coindcidentally is the same as the bacterial gene . and vertical evolution are correct.
E) endocytosis of the bacterium by the eukaryote and insertion of bacterial DNA into the eukaryotic DNA; resulting in vertical evolution.