A buffer solution results from mixing equal volumes of which solutions? I 0.10 M HCl and 0.20 M NH3 — Equilibrium Chemistry Question

A buffer solution results from mixing equal volumes of which solutions?
I 0.10 M HCl and 0.20 M NH₃
II 0.10 M HNO₂ and 0.10 M NaNO₂
III 0.20 M HCl and 0.10 M NaCl