A solution of urea (mol. mass\[56g\text{ }mo{{l}^{-1}}\]) boils at \[100.18{}^\circ C\] at the atmospheric pressure. If \[{{K}_{f}}\] and \[{{K}_{b}}\] for water are 1.86 and \[0.512K\text{ }kg\text{ }mo{{l}^{-1}}\] respectively, the above solution will freeze at

• A. \[0.654\text{ }{}^\circ C\]
• B. \[-0.654\text{ }{}^\circ C\]
• C. \[6.54\text{ }{}^\circ C\]
• D. \[-6.54{}^\circ C\]