In compound microscope, magnification does not depend upon
A. Focal length of lens
B. Numerical apertures of objective lens
C. Tube length of microscope
D. All of the above

Hint: A compound microscope uses two lenses which are the objective lens and eyepiece. When a small object is placed beyond the focus of an objective lens, you can see a highly magnified, virtual and inverted image of the object at least distance of distinct vision from the eye. By using a compound microscope, great detailing of various small objects can be obtained very clearly.

Complete answer:
> Focal length of lens: Focal length has some relation to do with magnification. A higher focal length results in a high magnification factor. The more long focal length is, narrow will be the angle of view and hence there would be increase in the magnification. Wide angle of view will result in low magnification.

> Numerical apertures of objective lens: It estimates the resolving power of an objective. It has the ability to gather light and to resolve fine details of any specimen that is to be observed. It does not relate to the magnification.

> Tube length of microscope: The tube body of the microscope separates the objective lens and the eyepiece. It also checks for the alignment of the optics. Changes in the objective lens are made depending on the particular projection distance which is very specific to the magnification. Therefore, it does depend on magnification.

Hence, the correct answer is option (B).

Note: Compound microscope is very easy and convenient to use. It has multiple lenses that makes it more special because great detailing can be observed by using it. These microscopes allow magnification to a much greater extent compared to stereo or light microscopes. However, one might face problems in having an image with big contrast.