The correct answer is Rigid and narrow-minded.
Indeed, Mr. Gradgrind is a firm and adamant proponent of Utilitarianism a philosophical doctrine that expresses that the highest ideal is utility and that all actions aim to the accomplishment of such ideal. Notions like beauty, leisure and other abstract concepts are not considered “useful”, they lack utility and thus are considered as a waste of time.
Dickens used this character as a representative of the way Industrial, Victorian England broke or ground the souls of people and in this particular case, children.