c
Basic buffer is mixture of weak base and salt of weak base with strong acid

milli mole of \(\mathrm{HCl}=100 \times 0.1=10\) milli mole

milli mole of \(\mathrm{NH}_{4} \mathrm{OH}=200 \times 0.1=20 \mathrm{mill}\) imole

\(\mathrm{HCl}+\mathrm{NH}_{4} \mathrm{OH} \rightarrow \mathrm{NH}_{4} \mathrm{Cl}+\mathrm{H}_{2} \mathrm{O}^{-}\)

\(10 \quad \quad \quad 20\quad \quad \quad \quad -\quad \quad -\)

\(-\quad \quad \quad 10\quad \quad \quad \quad  10\quad \quad \quad -\)