Final answer:
Evaporation leads to an increase in the osmotic pressure in the blood due to a higher solute-to-water ratio, affecting blood plasma osmolarity and blood pressure. Correct option is C.
Step-by-step explanation:
When an animal loses water by evaporation, the osmotic pressure in the blood increases. This is because evaporation leads to a reduction in the total volume of water in the blood, while the concentration of solutes (like salts and other electrolytes) remains the same.
The result is a higher solute-to-water ratio, which, according to the principles of osmosis, increases the osmotic pressure. In biological systems, such as those of mammals, osmotic pressure is crucial for maintaining the balance of fluids across cell membranes. Thus, the loss of water through evaporation can have a significant effect on blood plasma osmolarity, and by extension, blood pressure.