What is the solubility of a gas in water at $25^{\circ} C$ if the partial pressure is $0.18 \ atm$? $(K_{H} = 0.16 \ mol \ dm^{-3} \ atm^{-1})$

Which of the following gases is least soluble in water at the same temperature and pressure?

At $T \ (K)$ the molarity of $CO_2$ (in $mol \ L^{-1}$) in $200 \ mL$ of soda water packed under a pressure of $3.4 \ bar$ is ($K_H$ of $CO_2$ in water is $1.7 \times 10^3 \ bar$ at $T \ (K)$).

At $298 \ K$,how many millimoles of $CO_2$ gas will dissolve in $900 \ mL$ of water when $CO_2$ gas is passed through it? The $K_H$ value is $6.02 \times 10^{-4} \ bar$ and the partial pressure of $CO_2$ gas is $2 \times 10^{-8} \ bar$.

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Helium is used to dilute oxygen in diving apparatus.
Reason $R$: Helium has high solubility in $O_2$.
In the light of the above statements,choose the correct answer from the options given below:

Explain the equilibrium of gases in liquids.