Choose the correct statement.

The $$K_{\mathrm{H}}$$ value ($$\mathrm{K}$$ bar) of argon (I), carbondioxide (II), formaldehyde (III) and methane (IV) are respectively $$40.3,167, 1.83 \times 0^{-5}$$ and 0.413 at $$298 \mathrm{~K}$$. The increasing order of solubility of gas in liquid is

The vapour pressure of pure liquids $$A$$ and $$B$$ are 450 and $$700 \mathrm{~mm}$$ of $$\mathrm{Hg}$$ at $$350 \mathrm{~K}$$ respectively. If the total vapour pressure of the mixture is $$600 \mathrm{~mm}$$ of $$\mathrm{Hg}$$, the composition of the mixture in the solution is

Which of the following pair of solutions is isotonic?