Question

1. why should you not use the coarse focusing knob when using high power magnification?

it may scratch the lens.
it can break the glass on the slide.
it can displace the slide.
both a and b are correct.

Explanation:

When using high - power magnification, the objective lens is very close to the slide. Using the coarse focusing knob can cause the lens to move too much. If the lens moves too close to the slide, it may scratch the lens (option A) or break the glass on the slide (option B). So both A and B are correct.

Answer:

D. Both A and B are correct.