Explanation

The osmotic pressure is calculated using the formula $\pi = CRT$, where $C$ is molarity (1 mole/22.4 L = 0.0447 M), $R$ is the gas constant ($0.0821 ext{ L atm/mol K}$), and $T$ is temperature in Kelvin ($273.15 ext{ K}$). B is correct because $\pi = (1/22.4) \times 0.0821 \times 273.15 \approx 1$. A is incorrect because the calculation yields a value closer to 1, not 0.5. C is incorrect because the calculated pressure does not equal 1.5 atm. D is incorrect because the calculated pressure does not equal 2 atm.