Which of the following will produce a buffer solution when mixed in equal volumes?

• A

  $0.1 {\mathrm{moldm}}^{-3}{\mathrm{NH}}_4\mathrm{OH}\text{ and }0.1 {\mathrm{moldm}}^{-3}\mathrm{HCl}$

• B

  $0.05 {\mathrm{moldm}}^{-3}{\mathrm{NH}}_4\mathrm{OH}\text{ and }0.1 {\mathrm{moldm}}^{-3}\mathrm{HCl}$

• C

  $\text{ 0.1mol }{\mathrm{dm}}^{-3}{\mathrm{NH}}_4\mathrm{OH}\text{ and }0.05 {\mathrm{moldm}}^{-3}\mathrm{HCl}$

• D

  $0.1 {\mathrm{moldm}}^{-3}{\mathrm{CH}}_4\mathrm{COONa}\text{ and }0.1 {\mathrm{moldm}}^{-3}\mathrm{NaOH}$