Reaction of $NaCl$ with conc. $H_2SO_4$ liberates a gas,$X$ that turns moist blue litmus paper red. When gas $X$ is passed into a test tube containing egg shell powder suspended in water,another gas,$Y$ is generated which when passed through lime water makes it milky. The gases $X$ and $Y$,respectively,are

• A
  $HCl$ and $CO_2$
• B
  $Cl_2$ and $CO_2$
• C
  $SO_2$ and $CO_2$
• D
  $SO_2$ and $HCl$