If $1 \, L$ flask contains $O_2$ at a pressure of $7.6 \times 10^{-10} \, mm \, Hg$ at $0 \, ^\circ C$,then the number of $O_2$ molecules will be ......

• A
  $7.76 \times 10^{-10} \, N_A$
• B
  $4.46 \times 10^{-14} \, N_A$
• C
  $4.46 \times 10^{-10} \, N_A$
• D
  $7.76 \times 10^{-14} \, N_A$