The correct answer is option B, that is, functional group.
A functional group refers to a part of a molecule, which is a classified/recognizable group of bound atoms. The functional group provides the molecule with its characteristics, in spite of what molecule comprises it, they are the centers of chemical reactivity. The functional groups in a molecule require to be determined when naming.
Like all animals the noises they make are to warn off predators, and mating call. IDk
