I would recommend to move the slide away from the end of the viewing part of the microscope, so that if the lab partner were to adjust too much, that the viewing part of the microscope wouldn’t collide and passively crack the slide.
I don't really understand your statement
The cell wall contains not only cellulose and protein, but other polysaccharides as well. The cell wall provides structural support and protection. Pores in the cell wall allow water and nutrients to move into and out of the cell. The cell wall also prevents the plant cell from bursting when water enters the cell.
controll is your awser you vary a factor to measure the results