A student is preparing to observe a stained blood smear slide under a light microscope at high magnification using a 100× 100\times\,100× oil-immersion objective lens.
Which of the following procedures should the student use to safely and correctly focus the specimen?
Focus the specimen under a lower power lens, place a drop of immersion oil directly on the 100×100\times100× objective lens, click the lens into place, and use the coarse adjustment knob to lower the stage while looking through the eyepiece.
Focus the specimen under a lower power lens, rotate the nosepiece halfway, place a drop of immersion oil directly on the slide, click the 100×100\times100× objective lens into position in the oil, and use only the fine adjustment knob to focus.
Place a drop of immersion oil directly on the slide, click the 100×100\times100× objective lens into position, and use the coarse adjustment knob to raise the stage while looking through the eyepiece until the lens is submerged in the oil.
Rotate the 100×100\times100× objective lens into position, place a drop of immersion oil on the lens, raise the stage using the coarse adjustment knob while looking through the eyepiece, and then use the fine adjustment knob to focus.