Which one of the following aqueous solution posses lowest vapour pressure?

$\begin{array}{1 1}(a)\;\text{0.1M sugar}\\(b)\;\text{0.1M glucose}\\(c)\;0.1M\;BaCl_2\\(d)\;0.1M\;NaCl\end{array}$

Lowering of vapour pressure is directly proportional to the van't Hoff factor
Among all the compound $BaCl_2$ has highest van't Hoff factor $i=3$.
Hence (c) is the correct answer.
edited Jul 16, 2014