The correct answer is , Explanation & Key Takeaways: • Both mitochondria and chloroplasts possess their own genetic material thus, they are called semi-autonomous organelles. • The mitochondrial DNA and plastid DNA possess genes that produce the proteins necessary for the functioning of mitochondria and chloroplasts respectively. Important Notes: • Mitochondria (sing.: mitochondrion), unless specifically stained, are not easily visible under the microscope. • The number of mitochondria per cell is variable depending on the physiological activity of the cells. • In terms of shape and size also, a considerable degree of variability is observed. • Typically it is sausage-shaped or cylindrical having a diameter of 0.2-1.0µm (average 0.5µm) and length 1.0-4.1µm. • Each mitochondrion is a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments, i.e. the outer compartment and the inner compartment.