List the optical parts of the microscope

Eyepiece lens: the lens at the top that you look through. They are usually 10X OR15X  

Tube: connects the eyepiece to the objective lenses  

Arm : supports the tube and connects it to the base  

Base : the bottom of the microscope, used for supports  

Illuminator: a steady light source used in place of a mirror. If your microscope has a mirror, it is used to reflect light from an external light source up through the bottom of the stage.

Stage: the flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage, you will be able to move the slide around by turning two knob one moves it left and right ,the other moves it up and down.

Revolving: this is the parts that holds two or more objective lenses and can rotated

To easily to change power.

And there are so many objective  

Objective lense  

the correct answer to this question is #5