Why does dry HCl gas not change the colour of the dry litmus paper?

[A] Because dry litmus paper is not an indicator

[B] Because HCl gas is a weak acid, we must use a strong acid

[C] Because dry HCl gas does not ionize to produce H+ ions

[D] None of the above

Answer & Explanation
Answer: Because dry HCl gas does not ionize to produce H+ ions