Answer:
The revolving nosepiece because its function is to move the objectives in the microscope
Explanation:
Sometimes, if the stage is set high enough, the objective lens can hit or scratch the slide when it's changed, because each objective lens is a different length. From the back of the microscope, you cannot see if the lens is going to hit the slide or not, and run the risk of disturbing your sample. This problem can be prevented by looking from the side and stopping if it looks like the lens is going to hit the slide.
