For which one of the following mixtures is composition uniform throughout?

The swelling in feet and ankles of an aged person due to sitting continuously for long hours during travel, is reduced by soaking the feet in warm salt water. This is because of

A sample of water is found to contain $$5.85 \%$$ $$\left(\frac{w}{w}\right)$$ of $$A B$$ (molecular mass 58.5 ) and $$9.50 \%$$ $$\left(\frac{w}{w}\right) X Y_2$$ (molecular mass 95). Assuming $$80 \%$$ ionisation of $$A B$$ and $$60 \%$$ ionisation of $$X Y_2$$, the freezing point of water sample is [Given, $$K_f$$ for water $$1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$$, Freezing point of pure water is $$273 \mathrm{~K}$$ and $$A, B$$ and $$Y$$ are monovalent ions.]

Solubility of a gas in a liquid increases with