下列哪项属于无线连接（）A、双绞线B、同轴电缆C、地球卫星通信D、电话线E、光纤

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. ______小题1:____.
Nature is people’s good friend. It once helped people find fire, when lighting hit a forest and started a fire. _____小题2:___. 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.
___小题3:____ . When they got a fire from the forest, they tried to keep it burning. If it went out, they had to wait for ye小题4:ars.
_____小题5:___. For example, they made fire by boring 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. ____小题6:______

But later they found different way to make fire. The skins keep them warm. They can make fire at any time they need. People took some of this fire to their homes. People didn’t know how to use fire. But people still didn’t know how to make a fire.