The endosymbiont theory holds that mitochondria were originally bacteria-like single-celled organisms. Which of the following facts support this theory?

Mitochondria carry out aerobic respiration.
Mitochondria have their own DNA.
Different cells contain different numbers of mitochondria.
Mitochondria reproduce themselves independently.
A.
III and IV only
B.
II and IV only
C.
I and II only
D.
I, II, III, and IV