I believe that b is the answer
Speech understanding would have an effect hugely particularly
if the hearing loss is merely in one range. This would let the person to not pick
up or hear some letters articulated and perhaps not be able to put them
together. For instance, l, m, and n are central range pitches and s and f are high
range pitches.
At this point, the most important legal issue at the trial
is Zack’s mental competency of which the individual is either stable or
unstable and whether his mental capabilities are able to represent himself to
the trial of which will affect the issue if he wasn’t able to do so that it
could produce a more different effect on the trial.