III.1. This is the first time I have ever been to Sa Pa

2. I haven't seen him since 2010

3. It's the most beautiful sight she has ever seen

4. The weather in Sydney is not as hot as the weather in RdJ

5. They have lived in New York since 2004

6. The last time we went to Hanoi was 3 years ago

7. Big Ben is the most famous tower in England

8.  New York is much more modern than London.

IV. 1. more crowded  2. the most romantic 3. more expensive  4. the most famous  5. the biggest  6. more interesting  7. hotter  8. the most beautiful 

V. 1. b   2. d 3.c