What objective must be in place when you remove a slide or place a new slide on the stage of your scope 4x 40x or 10x?

When removing or placing a new slide on the stage of a microscope at 4x, 10x, or 40x magnification, the objective should be set to the lowest power (usually 4x) to ensure proper clearance and avoid damaging the slide or the objective lens. This allows for easier positioning of the slide and prevents potential collisions between the slide and the lens. Once the slide is securely in place, you can then switch to a higher magnification for detailed observation.