The correct option is D 0.1 M BaCl2
We know that, relative lowering of vapour pressure can be expressed by formula,
Po−PsPo=i×Xsolute
⇒Po−PsPo∝i
(a) Urea is a non-electrolyte. It does not dissociate into its ions in aqueous solution. Hence, i=1.
(b) Glucose is a non-electrolyte. It does not dissociate into its ions in aqueous solution. Hence, i=1.
(c) MgSO4 dissociate as Mg2+ and SO2−4. Hence, i=2.
(d) BaCl2 dissociate as Ba2+ and 2Cl−. Hence, i=3.