The correct statement about using a microscope is:
When changing magnification levels, make sure you do not remove the slide from the stage.
This is important to ensure that the sample remains in place and properly aligned under the objective lens as you adjust magnification.
Additionally, while using the course and fine focus knobs is important for obtaining a clear image, a combination of both focusing methods must be done carefully. Typically, you would start with the lowest magnification and then use the coarse focus knob initially, followed by the fine focus for clarity.
If you would like, I can clarify further about proper microscope use!