根据句意和汉语注释，在横线上，写出单词的正确形式。

1. As we know, oil always __________ (漂浮) on water.

2. He __________ (点头) to me in greeting when I entered the room.

3. We are very __________ (自豪) that a pupil from our school has won the prize.

4. They all hurried __________ (往楼上) to see what was going on.

5. There was __________ (沉默) for a moment and then someone made a useful suggestion.