Answer:
D. Separate ecosystems can affect each other.
It form the contraction and relaxation of muscle
<span>The circulatory, immune, skeletal, excretory, muscular, endocrine, digestive, nervous and respiratory. those are the eight systems of the human body.</span>
The endoplasmic reticulum can either be smooth or rough, and in general its function is to produce proteins for the rest of the cell to function. The rough endoplasmic reticulum has on it ribosomes, which are small, round organelles whose function it is to make those proteins.
