Answer:
The correct answer would be D. species.
Natural taxon refers to the group of organisms which exists in nature as a consequence of evolution.
In Linnaeus's system, the only natural taxon is "species".
Species refers to the group of organisms in which two organisms of opposite or appropriate genders can produce a viable offspring.
<span>The movement along the concentration gradients allows for the cell to maintain homeostasis. Keeping a cell in the proper conditions inside and out allows for it to function properly and carry out the duties that it is required to do as part of its bodily system.</span>