Choose the incorrect statements with respect to mitochondria.
I. Mitochondria are easily visible under microscope in unstained preparations. 
II. Mitochondria are cylindrical or sausage shaped.
III. The outer compartment of mitochondrion is called matrix.
IV. Infoldings of inner membrane are called as cristae.
 

Mitochondria are visible under microscope when stained with janus green. In unstained preparations mitochondria are not clearly seen as mitochondria have same refractive index as that of surrounding cytoplasm. The outer compartment of mitochondrion is called peri-mitochondrial space and the inner compartment is matrix. Cristae are the infoldings of inner membrane.