A solution of $\ce{KNO3}$ in water is prepared for which the following data have been obtained:
\[ \text{masses of solute and solvent} \]
\[ \text{molar masses of solute and solvent} \]

Which of these quantitative descriptions of the solution can be determined?

\[ \text{I. molarity II. molality III. density of solution} \]

$ \textbf{(A) }\text{I. only}\qquad\textbf{(B) }\text{II. only}\qquad\textbf{(C) }\text{I. and II. only}\qquad\textbf{(D) }\text{I., II. and III.}\qquad$
To determine which quantitative descriptions of the solution can be determined, let's analyze each option given the data provided:

1. **Molarity (I)**:
   - Molarity (M) is defined as the number of moles of solute per liter of solution:
     \[
     M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}
     \]
   - To calculate molarity, we need the volume of the solution. Since the problem does not provide any information about the volume of the solution, we cannot determine the molarity.

2. **Molality (II)**:
   - Molality (m) is defined as the number of moles of solute per kilogram of solvent:
     \[
     m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}}
     \]
   - Given the masses of the solute and solvent, and the molar masses of the solute and solvent, we can calculate the number of moles of solute and the mass of the solvent in kilograms. Therefore, we can determine the molality.

3. **Density of solution (III)**:
   - Density (ρ) is defined as the mass of the solution per unit volume:
     \[
     \rho = \frac{\text{mass of solution}}{\text{volume of solution}}
     \]
   - To calculate the density, we need the volume of the solution. Since the problem does not provide any information about the volume of the solution, we cannot determine the density.

Based on the analysis, we can only determine the molality of the solution.

The final answer is $\boxed{\textbf{(B)}}$