Energy makes the world go round. Energy lights our cities. Energy powers our vehicles (交通工具), trains,     16     and rockets. Energy warms our homes, cooks our food, plays our music, gives us pictures on television. Energy powers machines in factories and tractors on a farm. Without it, we’d be without key forms of technology and transportation.

Energy from the sun gives us light during the day. It dries our clothes     17     they’re hanging outside on a clothes line. It helps plants grow.

Everything we do     18     energy in one form or another.

When we eat, our bodies change the energy stored in the food into energy to do work. When we run or walk, we “burn” food energy in our bodies. When we think or read or write, we are also doing work. Many times it’s really hard work!

Cars, planes, light bulbs, boats and machines also     19     energy into work. Work means moving something, lifting something, warming something, lighting something. All these are a few of the various types of work.

Electricity is a     20     of energy used in our lives every day. Here’s something you can do to see the importance of electricity. Take a walk through your school, house or apartment and write down all the different appliances and machines that use electricity. You’ll be     21     at how many things we use each and every day that depend on electricity.