根据汉语提示填入单词的适当形式。
1. Robert enjoys _____ (收集) stamps. And now he has 300 of them.
2. She will be the _____ (第五个) to speak at the meeting.
3. I am really sorry I was late. I just _____ (错过) the early bus this morning.
4. Nancy is _____ (在楼下). Go and find her yourself.
1. collecting 2. fifth 3. missed 4. downstairs