Among the following gases which gas has the highest Henry's law constant, ${\mathrm{K}}_{\mathrm{H}}$ value in water at the same temperature?

 Henry's law states that, the amount of gas dissolved, or the solubility of this gas will be directly proportional to the partial pressure at a given temperature.

From the given formula,

$P=K_H\times C$

By rearranging these terms, we get:

$K_H=\frac{P}{C}$ where, $P$ is the partial pressure, $K_H$ is Henry's law constant and $C$ is the concentration of gas dissolved.

 From this above equation we know that the solubility of the gas is inversely proportional to Henry's law constant.

$K_H\propto \frac{1}{C}$

This means that a gas is easily soluble in water, which would result in more amount of the gas dissolving in water, which would lead to a rise in its concentration and hence the Henry's law constant should decrease.

therefore, for a gas to have a high value of Henry's law constant, it should have very less solubility in water.

Hence the Value of Henry's law constant in decreasing order will be:

$He>N_2>H_2>O_2$

Hence, option(d) is correct answer.