Concept:Children who cannot speak or hear use sign language to communicate and learn.Explanation:Children who cannot hear often cannot speak naturally. They need an alternative way to understand and express ideas.Sign language uses hand gestures, facial expressions, and body movements. It is a complete visual language.Teachers should learn common signs and teach them to such children. Lip-reading may also help if the child has some hearing.Using local or native spoken language will not work because the child cannot hear. Braille is for the blind, not for deaf or mute children.Answer:A. through sign language