A buffer solution made with ${\mathrm{NH}}_3$ and ${\mathrm{NH}}_4\mathrm{Cl}$ has a $\mathrm{pH}$ of 10.0. Which procedure(s) could be used to lower the $\mathrm{pH}$?

1. Adding HCI   2. Adding ${\mathrm{NH}}_3$

3. Adding ${\mathrm{NH}}_4\mathrm{Cl}$