Exactly one of these statements is false. Which one?
(a) When ammonia dissolves in water, the latter behaves as a Lewis base.
(b) The conjugate acid of $\ce{H-}$ is $\ce{H2}.$
(c) Boric acid is a monobasic acid.
(d) Ammonia behaves as an acid when it reacts with sodium metal to give sodamide and hydrogen.
The key says (d) is the false statements. How? I think (a) is the one.
(d) $\ce{2NH3 + 2Na -> 2NaNH2 + H2}$
The ammonia here loses a proton, which is characteristic for acids. In addition, it attaches to the electropositive sodium.
(a) On the other hand, when ammonia dissolves in water:
$\ce{NH3 + H2O <=> NH4+ + OH-}$
Ammonia gains a proton, which is characteristic for bases.