What is the cervical groove?

semiricular notch that dives the head of the crayfish from the abdomen

many phylogenetic trees have a single lineage at the base representing a common ancestor. a lineage that evolved early from the root and remains unbranched is called basal taxon. when two lineages stem from the same branch point, they are called sister taxa.

can i get the brainliest pls

explanation:

if you listed your answers right then i believe your answer is b.