Final answer:
A solution that freezes at -1.98°C is isotonic to plasma, meaning it has the same osmolarity and thus avoids undesirable exchange of materials with the blood cells.
Step-by-step explanation:
A solution freezing at -1.98°C would be isotonic to plasma if its solute concentration allows for no net movement of water into or out of the cells. Plasma typically has a freezing point close to that of water, which is 0°C, but the presence of solutes in plasma lowers its freezing point. Isotonic solutions, which have the same osmolarity as plasma, are often used in medical situations to ensure that red blood cells maintain a normal volume and shape without shrinking (crenation) or swelling and rupturing. For a solution to be isotonic with human plasma, it should typically be a 0.9% m/v NaCl or a 5% m/v glucose solution in water.
Therefore, the correct answer to the question is B. The solution is isotonic to plasma. Isotonic solutions are crucial for intravenous (IV) therapy, as they avoid the exchange of materials to or from the blood in an undesirable way, preserving the cells' integrity.