Air is a mixture of a number of gases. The major components are oxygen and nitrogen with approximate proportions of $20\%$ and $79\%$ by volume at $298\ K$. The water is in equilibrium with air at a pressure of $10\ atm$. At $298\ K$,if the Henry's law constants for oxygen and nitrogen are $3.30 \times 10^7\ mm$ and $6.51 \times 10^7\ mm$,respectively,the mole ratio of gases $(O_2 : N_2)$ dissolved in water is about

• A
  $1 : 2$
• B
  $2 : 1$
• C
  $1 : 8$
• D
  $1 : 3$