Your classmate is viewing a sample using high power and is about to refocus using the coarse adjustment knob. What would you recommend your classmate do and why?

Using the coarse adjustment knob of the microscope in high power may lead to the breaking of the slide if adjusted and raised the slide too much which can damage the sample as well as the high power lens.

In this case, I would recommend using the fine adjustment knob and moving away from the end of the viewing area of the microscope so there would no collision take place. The fine adjustment will help to get a clear image.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.