Which from following gases is least soluble in water under same conditions of temperature and pressure ?

Calculate the molality of aqueous solution of electrolyte that freezes at $-0.93\,^\circ\text{C}$ if $K_f$ for water and van't Hoff factor respectively are $1.86\,\text{K kg mol}^{-1}$ and $1.25$. (Freezing point of water $= 0\,^\circ\text{C}$ )

Calculate the solubility of certain gas in solvent with pressure $3$ atm at $25^\circ\text{C}$ (Henry's law constant is $3.0 \times 10^{-2}\,\text{mol dm}^{-3}\,\text{atm}^{-1}$)

Which among the following pairs of solutions is isotonic in nature?