The answer is ..b .the smallest units of an element ...
Hope it helps !!!
The mitochondria isn't considered to be part of the endomembrane system because its structure is not derived from the nuclear envelope, ER, GolgiApparatus, or cell membrane.
Phase 1: Starts with the separation between populations. Separated populations become adapted to local conditions and become genetically differentiated over time.
Phase 2: Genetic isolation is completed, reproductive isolation develops mostly in the forms of prezygotic RIMs.
They get outta hand and organize