重点短语
1. the highest mountain in the world (Qomolangma)世界上最高的山
2. the biggest desert in the world (the Sahara)世界上最大的沙漠
3. the longest river in the world (the Nile)世界上最长的河
4. the deepest of all the salt lakes (the Caspian Sea)所有咸水湖中最深的
5. the biggest population in the world世界上最大的人口数量
