It was a case of emergency．The four-year-old girl awoke and smelled smoke．She couldn"t wake her mother,so she dialed"zero",An operator immediately called the fire department．Help was sent,and a tragedy avoided. Days before this emergency,the mother had taught her child how to telephone for help．Children as young as two and one-half years old can be taught to use the phone in emergency situations．Here are some points. Memorizing certain facts is important．Teach your children their names,and the section of town where you live．Try to keep what they learn within their abilities．Simple information,learned well,is better than difficult information only partly learned. Be sure your children know how to use the telephone．They should be taught to dial"zero"for the operator,at the very least．And they should be taught to dial"911"if it is used in your town. Practice over a period of several days．Over-learning is necessary so the child can act automatically in case of emergency. If you would like a booklet giving instructions on calling for help,write Telephone For Help,Box 99,Bowling Green Station,New York,NY 10004. What is the main idea of the passage?