Two statements are given below.
Statement-$I$: Adsorption of a gas on the surface of charcoal is primarily an exothermic reaction.
Statement-$II$: $A$ closed vessel contains $O_2, H_2, Cl_2, NH_3$ gases. Its pressure is $P \ atm$. About $1 \ g$ of charcoal is added to this vessel and after some time its pressure was found to be less than $P \ atm$.
The correct answer is:

• A
  Both statement-$I$ and statement-$II$ are correct.
• B
  Both statement-$I$ and statement-$II$ are not correct.
• C
  Statement-$I$ is correct but statement-$II$ is not correct.
• D
  Statement-$I$ is not correct but statement-$II$ is correct.