1. This is the biggest flood in a century. (bigger)
There's no flood in a century is as big as This flood
2. The test wasn't as easy as she'd expected. (than)
The test was more dificult than she'd expected.
3. I can let you in if you give the password. (unless)
I can't let you in unless you give the password
4. He slipped out during the conference. (having)
While we having a conference , He slipped out
5. It is cheaper to go by bus than to go by taxi. (expensive)
Going by taxi is more expensive than going by bus