Identify the unclear pronoun references in the following paragraph. Where necessary, rewrite the sentences so that all pronoun references are clear: - Autism is a physical disorder of the brain who causes a lifelong developmental disability. Unfortunately, a number of boys and girls become victim of it after their birth. Children with autism vary widely in their activities, abilities, behaviours, etc. and the symptoms may appear differently in him. The sorrows and sufferings of the parents of those know no bounds. Though the autistic children are quite different in activities from the normal children, they should not be neglected. Rather, we have a great responsibility towards them.