Thousands of years ago, people didn't live in cold places because they didn't know how to keep themselves warm. Later they learned to make clothes. When an animal was killed, they made use of its skins to cover their bodies.     .
   . It once helped people find fire, when lighting hit a forest and started a fire.        The fire kept them warm, and also frightened wild animals. Soon people found the food cooked tasted much better, so they began to use the fire to cook food.
But people still didn't know how to make a fire. When they got a fire from the forest they tried to keep it burning.    
But later they found different ways to make fire. For example, they made fire by burning wood or knocking two pieces of stones.
Today it's easy for people to make fire because they have matches, lighters and different kinds of heaters.   
根据短文内容，把A-E五个选项填入文中空缺处，使短文内容完整、正确。

A．If it went out, they had to wait for years.

B．The skins keep them warm.

C．They can make fire at any time they need.

D．People took some of this fire to their homes.

E. Nature is people's good friend..