Which from following pairs of solutions in water exhibits same osmotic pressure at same temperature ?
\(\left[\right.\) molar mass of urea \(=60 \mathrm{~g} \mathrm{~mol}^{-1}\), sucrose \(\left.=342 \mathrm{~g} \mathrm{~mol}^{-1}\right]\)

1. A \(3 \mathrm{~g} \mathrm{~L}^{-1}\) urea and \(17 \cdot 1 \mathrm{~g} \mathrm{~L}^{-1}\) sucrose
2. B \(6 \mathrm{~g} \mathrm{~L}^{-1}\) urea and \(17 \cdot 1 \mathrm{~g} \mathrm{~L}^{-1}\) sucrose
3. C \(3 \mathrm{~g} \mathrm{~L}^{-1}\) urea and \(34.2 \mathrm{~g} \mathrm{~L}^{-1}\) sucrose
4. D \(6 \mathrm{~g} \mathrm{~L}^{-1}\) urea and \(8.6 \mathrm{~g} \mathrm{~L}^{-1}\) sucrose