A student carried out an investigation into the diffusion of ammonia gas, $\text{NH}_3$, and hydrogen chloride gas, $\text{HCl}$. At room temperature and pressure, two sets of apparatus were arranged as shown. In apparatus 1, the damp red litmus paper changed colour after $30$ seconds. How long does the damp blue litmus paper take to change colour in apparatus 2?
- A64 seconds
- B30 seconds
- C21 seconds
- DThe blue litmus paper would not change colour.