Why is your desk （tidy）？
Because I painted a picture there just now．
The Great Wall is too high． I have difficulty （climb） it alone．
The teachers welcome their students （polite） at the school gate every morning．
After doing sports for months， Tina is becoming （thin） than before．
Forty （year） development has changed Huai'an into a modern city．
To my surprise， my uncle got his driving licence in his （fifty）．