根据所给汉语提示，写出空缺处单词正确形式。
1. _____ (突然) he heard someone crying for help.
2. Yesterday the grandfather bought a _____ (兔子) for his grandson.
3. Mary is going to have a birthday _____ (聚会) next week
4. There is a _____ (洞) on the wall.
5. When he went to the America at first, he felt _____ (陌生的).
