Which adjustment knob is used for bringing the specimen into focus

The coarse adjustment knob is for focusing of the slide.

Explanation:

Coarse Adjustment Knob - The coarse adjustment knob built on the arm of the microscope is for moving the stage up and down to bring the specimen into focus.

Note:

Fine Adjustment Knob - is inside the coarse adjustment knob and is used for sharp focusing of the specimen under low power and is used for all focusing when high power lenses is used.