[单选题]
3. Which of the following appara-yrc 9t1 9l)kgxz2eqetus a;.h9j jmutic:nd techniques was used in determining the function of individual orhj mui: j.;tc9ganelles?
I. Fractionation.
II. Ultracentrifugation.
III. Electron microscopy.
IV. Light microscopy
A. All of the above.
B. I, II and IV only.
C. I only.
D. II only