Although you are young，you can （仍然） make the world more beautiful in your own way．
Our government has made laws to （限制） air and water pollution．
If you go to ，you'd better not miss the Opera House in Sydney．
All children between the age of 5 and 16 in his country must （go to）school．
Please put the book back to its （right or correct）place after you read it．