The correct option is A An electric bell
An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing or clanging sound. Electric bells have been widely used at railroad crossings, in telephones, fire and burglar alarms, as school bells, doorbells, and alarms in industrial plants, since the late 1800s, but they are now being widely replaced with electronic sounders. It consists of coils of insulated wire wound round iron rods. When an electric current flows through the coils, the rods became magnetic and attract a piece of iron attached to a clapper. The clapper hits the bell and makes it ring.