Which of the following pictures reflects the effect on red blood cells when plain water is infused into a person?

S-19-B.PNG is incorrect. This image might depict red blood cells in a hypertonic solution, where the concentration of solutes outside the cells is higher than inside. In this case, water would move out of the cells to balance the concentration, causing the cells to shrink, which is the opposite of what happens when plain water is infused.

S-19-C.PNG is also incorrect. This could represent red blood cells in an isotonic solution, where the concentration of solutes inside and outside the cells is equal. In this case, there would be no net movement of water and the cells would remain the same size, which does not reflect the effect of infusing plain water.

S-19-D.PNG is not correct either. This might represent a pathological condition of the red blood cells, like sickle cell anemia or another sort of irregularity. It does not represent the effect of infusing plain water into a person's bloodstream.