B) its a weak acid, hence does not completely dissociate. As such, it is close to impossible to deduce the amount of NaOH needed to neutralise ethanoic acid and hence produce the endpoint (i.e. the H+ would be the partially ionised ones, and as such, all the OH- that reacts with this H+, will not equal the change in endpoint). Most likely, this will produce an endpoint quicker than what is required. Therefore, pH tests are more effective as they can deduce between acid strength and concentration as well (pH = -log H+)...