On heating a mixture of common salt and $K_{2}Cr_{2}O_{7}$ with concentrated $H_{2}SO_{4}$, a gas is evolved. The formula of the gas evolved and the oxidation state of the central metal atom in the gas, respectively, are:

• A
  $CrO_{2}Cl_{2}$ and $+5$
• B
  $CrO_{2}Cl_{2}$ and $+6$
• C
  $Cr_{2}O_{2}Cl_{2}$ and $+6$
• D
  $Cr_{2}O_{2}Cl_{2}$ and $+3$