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.