用括号中所给单词的适当形式填空。 1. Please call me if you have any problems __________ (work) out. 2. Marie Curie received the Nobel Prize __________ (two) during her life time. 3. I think it is __________ (danger) for children to be close to wild animals. 4. The old man has been __________ (die) since three years ago. 5. I know only one of the ___________ (visit), how about you?