Rewrite the sentences

10.- “Which is the most expensive city in the world ?” – “ I think it’s Tokyo.”.
Lan is the oldest of the three sisters       
Lan has ..........................................................................
4. It is wrong of us to throw rubbish..
We mustn’t …………
6. Learning how to use a computer is very easy
 It is …………………………
7. He drives very carefully
 He is  ..………….……