Which One of the Following Is the Conjugate Base Of \mathrm{NH}_{3}

Which one of the following is the conjugate base of $\mathrm{NH}_{3}$ ?

A) $\mathrm{NH}_{4}{ }^{+}$
B) $\mathrm{H}^{+}$
C) $\mathrm{N}^{3-}$
D) $\mathrm{NH}_{2}^{-}$