Answer:
D. Joel used all flasks to test the tonicity of the red blood cells, the solution with the same tonicity as the cells, would allow the cells to maintain roughly the same size
Step-by-step explanation:
The different concentration of salt will react with the red blood cell differently; in the presence of high salt concentration, the red blood cell will shrink (hypertonic environment) while in the presence of low salt concentration the red blood cell will swell (hypotonic environment) but if the red blood cell and the salt concentration is almost the same the cell will maintain almost the same size