用所给单词的适当形式填空。
1. Is the Great Wall one of                      (great) wonders of the world?
2. When the family had lunch, it                     (rain) outside.
3. When it became dark, there was nothing                    (see) in the room.
4. Look! There is a                     (strange) over there.
5. Is the Sydney Opera House a great wonder of the                      (nature) world?