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