题目内容：

    You might have noticed that sometimes, when you are playing mobile games, the picture suddenly freezes(卡顿)because the network speed is o slow. However, these annoying things will soon become a thing of the past, as China just issued commercial licenses (发放商用牌照）for 5G networks on June 6, 2019. This means that China's telecommunications companies will be able to offer 5G network speeds to users.

The "G" in "5G"stands for generation. IG let us talk to each other, 2G let us send messages, 3G gave us mobile data and internet, and 4G made all of these things faster. So what will SG bring?

It will allow us to download an entire HD movie in seconds. The delay(延时)between sending and receiving data will be shortened. Now, 4Gtakes about 100 to 200 milliseconds, while humans have a reaction time of about 200 to 300 milliseconds. But 5G will get the delay down to I millisecond or less, which is almost real—time.

With the development of 5G, new kinds of technology will be created and used.

Robots will be used to do operations because doctors will be able to control them from somewhere else without any delay. Self—driving cars will be able to drive more safely because they can smoothly communicate with each other, traffic lights and road sensors.

5G networks will be powerful, but not perfect. They do have some disadvantages.

On one hand, 5G signals don't go very far. On 4G networks, you can be 10 kilometers away from the nearest transmission base(传送基站）and don't lose signal. But 5G maxes out at about 300 meters. On the other hand, 5G signals have a hard time going through walls and rains. This means we will need to build many small transmitters to make sure 5G signals can be received everywhere. Soon you may see small boxes on every street lamp and building.

1.Why does the picture freeze when we are playing mobile games?

2.What does "G" in"5G"stand for?

3.How long will it take to download an entire HD movie with 5G?

4.What is the fourth paragraph mainly about?

5.What disadvantages do 5G networks have?