Write the correct comparative.

Solution:

1. A: This top is too big for me. I need a smaller (small) one.
   B: I'm sorry, this is the smallest size we have.
2. Tom is always smiling. He is the friendliest (friendly) person I know.
3. This book is more difficult (difficult) than the one we did last year.
4. When the traffic is heavy, it is more difficult (easy) to walk to work than drive.