根据句意,用所给词的正确形式填空。
1. We were all surprised at his _____ (arrive). We thought he wouldn't come.
2. I told myself _____ (calm) down since was still alive.
3. We must prevent people _____ (cut) down trees.
4. What a _____ (sun) day it is today!
5. Everyone should know the _____ (important) of protecting the wildlife.