Answer: option (A)Alligator and earthworm.
The alligator is a vertebrate, having spinal chord or backbone. The earthworm is invertebrates which means it lacks vertebral column.
Species organisms of different species share similarity in DNA sequence when they share most recent ancestor. Alligators and earthworms are distantly related organism as they belongs to different phylum and do not share a recent common ancestor.
On the other hand organisms in other options belong to same phylum so they will show more similarity between their nucleotide sequence. Thus, they will have the fewest similarity in DNA sequence of a given gene.
