Answer:
c. mitochondrion
Step-by-step explanation:
The mitochondrion is a double membrane-bound organelle present in eukaryotic cells only. It is the site for Kreb's cycle and oxidative phosphorylation and produces a large amount of energy stored in the form of ATP.
Since Kreb's cycle and oxidative phosphorylation are second and final stages of aerobic cellular respiration respectively, the mitochondrion is called a site of respiration in cells.