The mechanical stage upper knob causes the stage to move

Red blood cells are animal cells that lack a cell wall, a rigid structure that surrounds the cell membrane of plant cells, such as Elodea cells. A cell wall provides support and protection for the cell, and prevents excessive water uptake or loss. Red blood cells, on the other hand, rely on the osmotic balance of their environment to maintain their shape and function. If red blood cells are placed in a hypotonic solution, where the water concentration is higher outside than inside the cell, they will swell and burst due to osmosis. This is called hemolysis. If red blood cells are placed in a hypertonic solution, where the water concentration is lower outside than inside the cell, they will shrink and lose their ability to carry oxygen. This is called crenation.

Elodea cells, however, can withstand hypotonic or hypertonic solutions without bursting or shrinking, because their cell wall prevents the water from entering or leaving the cell beyond a certain point. Therefore, a major difference between red blood cells and Elodea cells is that Elodea cells have a cell wall, which protects them from bursting.

Choice A rationale: Movement of water into the blood from the dialysis solution is incorrect because it is not the main goal of dialysis. Dialysis aims to remove excess water and solutes from the blood, not to add more water to it. The dialysis solution is usually isotonic to the blood, which means it has the same osmotic pressure and does not cause water movement.

Choice B rationale: Simple diffusion across a semi-permeable membrane is correct because it is the process of dialysis. Dialysis is the separation of small molecules from large molecules by using a membrane that allows only the small molecules to pass through. The dialysis membrane is semi-permeable, which means it is selective in what it allows to cross. The dialysis solution contains a lower concentration of wastes than the blood, which creates a concentration gradient that drives the diffusion of wastes from the blood to the solution.

Choice C rationale: Active transport across a semi-permeable membrane is incorrect because it is not involved in dialysis. Active transport is the movement of molecules across a membrane against their concentration gradient, which requires energy and transport proteins. Active transport is not necessary for dialysis, since the concentration gradient is favorable for diffusion.

Choice D rationale: Active transport of glucose from the blood to the dialysis solution is incorrect because it is not beneficial for dialysis. Glucose is a vital nutrient for the body, and it should not be removed from the blood. The dialysis solution usually contains glucose to prevent its loss from the blood by diffusion.

Choice E rationale: Facilitated diffusion across a semi-permeable membrane is incorrect because it is not relevant for dialysis. Facilitated diffusion is the passive movement of molecules across a membrane with the help of transport proteins. Facilitated diffusion is not needed for dialysis, since the wastes are small enough to cross the membrane by simple diffusion.