The following text is for questions 20 to 26.

Trains

A train is made up of railroad cars, hooked together and pulled by a locomotive. Locomotives are sometimes called engines. The types of locomotive engines most used today are diesel-electric. Engines that burn diesel fuel drive generators that make electricity. Powerful electric motors turn the wheels of a diesel-electric locomotive. There are two types of train, freight and passenger trains.

A freight train can have as many as 200 cars hooked together. There are special railroad cars for different kinds of freight. The boxcar has four sides, a floor and a roof. It carries radios, television sets and boxes of cereal. Refrigerator cars work like your home refrigerator. They are boxcars that are cool inside. Refrigerator cars carry meat, fruit, frozen dinners and other food that must be kept cold. The hopper car is open on the top. Hopper cars carry coal, sand, gravel, and ore (rocks that contain metals). A flat car has no top or sides. It has a floor on wheels. Flat cars carry lumber, steel beams, huge pieces of machinery, and other big items. Lifting machines called cranes load cargo onto flat cars. Special flat cars carry cars, boats, and trucks.

Passenger trains have seats in rows along each side. They are made for long trips. They have seats that can be made into beds at night. Trains that carry passengers over long distances have special baggage cars to carry suitcases. They have dining cars where people can sit down and eat.

22. Which freight car is used to carry sand?