The $K_{H}$ values for some gases at the same temperature '$T$' are given below:

Gas	$K_{H} / \text{kbar}$
$Ar$	$40.3$
$CO_{2}$	$1.67$
$HCHO$	$1.83 \times 10^{-5}$
$CH_{4}$	$0.413$

where $K_{H}$ is Henry's Law constant in water. The order of their solubility in water is:

• A
  $Ar < CO_{2} < CH_{4} < HCHO$
• B
  $Ar < CH_{4} < CO_{2} < HCHO$
• C
  $HCHO < CO_{2} < CH_{4} < Ar$
• D
  $HCHO < CH_{4} < CO_{2} < Ar$