A solution containing `10 g per dm^(3)` of urea (mol.wt. `= 60 g mol^(-1)`) is isotonic with a `5%` ( mass//vol.) of a non-volatile solute. The molecular mass of non-volatile solute is:
A. `"300 g mol"^(-1)`
B. `"350 g mol"^(-1)`
C. `"200 g mol"^(-1)`
D. `"250 g mol"^(-1)`