Question

suppose you a viewing a slide using the scanning (4x) objective lens. which adjustment knob(s) can you safely use when this objective is in place? only the coarse adjustment knob only the fine adjustment knob both the coarse adjustment knob and the fine adjustment knob

Explanation:

When using the scanning (4x) objective lens (low - power objective), the coarse adjustment knob can be used to quickly bring the specimen into approximate focus, and the fine adjustment knob can be used for fine - tuning the focus. The risk of crashing the lens into the slide is low with the 4x objective, so both knobs can be safely used.

Answer:

Both the coarse adjustment knob and the fine adjustment knob