When using a Microscope's high power objective the course adjustment knob:

a. Can be used throughout the focusing process.
b. Can not be used with low power object
c. Can be used only with scanning
d. Objective should not be used

c. Can be used only with scanning

Explanation:

Coarse Adjustment Knob is a large knob on each side of the microscope, with a smaller knob in the middle. This large knob is used to bring an object into close focus as it moves the stage up or down. The coarse-adjustment knob is used ONLY with the scanning or low-power objective lenses.

The correct option is;

d. Objective should not be used

Explanation:

The coarse-adjustment knob is the large knob at the base of the Microscope close to the smaller fine-adjustment knob. The coarse-adjustment knob is meant to aid in the movement of the object into proper focus either upwards or downwards and is only meant to be used with the scanning, low power objective lenses.

When using the Microscope's high power objective lens, the field of view is narrower as such only the fine adjustment knob should be used.

an electric circuit