Final answer:
The red blood cell in an isotonic solution would be found in a human body during homeostasis, retaining its normal shape as the movement of water into and out of the cell is balanced.
Step-by-step explanation:
The red blood cell would retain its normal shape in an environment of homeostasis, specifically, within an isotonic solution. This is because the influx of water into the cell is equal to the outflux, maintaining equilibrium and preventing any detrimental changes to the cell's volume. If red blood cells were placed in a pure water environment, they would likely undergo hemolysis, as the hypotonic conditions would cause an excessive amount of water to enter the cells leading them to swell and eventually burst, since there are no mechanisms in red blood cells to prevent them from taking on too much water. However, within the human body, these cells are generally protected from such extremes as the body's regulatory systems maintain homeostasis, ensuring that the red blood cells are in an isotonic state as they travel through the bloodstream to carry out their principal job, which is to carry and deliver oxygen to tissues.