1.重点单词：square，meter，deep，desert，population，Asia，wall，tour，tourist，ancient，protect，wide
2．重点短语：manmade objects，as far as I know
3．重点句式：
Qomolangma is higher than any other mountain in the world.
What is the highest mountain in the world?
China has the biggest population in the world.It's a lot bigger than the population of the US.
It has a much longer history than the US.
China is almost as big as the US.
Did you know that China is one of the oldest countries in the world?
How long is the wall?
The main reason was to protect China.
As far as I know，there are no manmade objects as big as this.
Is Badaling part of the Ming Great Wall?
