Final answer:
Thicker smears with higher protein concentration benefit from longer staining times, while thin smears of fluids with low protein concentration do not.
Step-by-step explanation:
Thicker smears with higher protein concentration benefit from longer staining times. This is because the protein concentration affects the ability of the dye to bind to the cells. Thicker smears have more protein, so longer staining times allow for better dye binding and staining. On the other hand, thin smears of fluids with low protein concentration do not benefit from longer staining times because there is less protein available for the dye to bind to.