1. It is essential for him to buy a new bike
- He needs to buy a new bike 
2. We should travel by bike or bus to reduce the air pollution
- If we travel by bike or by bus, we would reduce the air pollution
3. I had a stomachache because of the polluted water
- The water pollution made my stomach hurt
4. I moved to this house in 2012
- I have moved to this house since 2012
5. This building is smaller than that building
- That building is bigger than this building 
6. My neighbourhood is noisier than your neighborhood
- Your neighborhood is not as noisy as mine
7. Himalayas is longer than other mountain ranges in the world
- Himalayas is the........longest mountain ranges in the world .......
8. The Green hotel is cheaper than the Palace hotel
- The Palace hotel ...is more expensive than the green hotel ......
9. Hoi An is more historic than Da Nang
- Da Nang........isn't as historic as Hoi An..
10. These streets are wider than those streets
- Those streets.........are narrower than these streets .........