When solid sodium hydride, NaH, is added to water, the hydride ion reacts according to the following equation - VCE - SSCE Chemistry - Question 7 - 2009 - Paper 1

The reaction presents characteristics of both acid-base and oxidation-reduction processes. In this reaction, the hydride ion ($H^-$) acts as a base by accepting a proton ($H^+$) from water, producing hydroxide ions ($OH^-$). This highlights the acid-base nature of the reaction. Additionally, the conversion of $H^-$ to $H_2(g)$ demonstrates a reduction process, as the hydride ion is oxidized to diatomic hydrogen. Therefore, the correct classification for this reaction is:

D. neither acid-base nor oxidation-reduction.

Since the hydride ion reaction specifically indicates proton donation and electron transfer, it does not solely fit into the categories provided.