The mechanical stage upper knob causes the stage to move which way

Right and left (X-axis)

Explanation:

This question is describing a microscope with a mechanical stage, which refers to the properties of the stage put in place to hold and move the slide. A mechanical stage consists of two knobs named X and Y knobs. They are so named after the direction in which they move the slide when used.

The X knob, which is the upper knob provides a clear view of the specimen by moving the slide in the X direction i.e. right and left. On the other hand, the Y knob moves the slide forward and backwards.