根据汉语提示用单词的适当形式填空
1. I’m so nervous because there are so many ________________(陌生人) in the room.
2. Have you ever _______________(梦想) of flying into space one 
day.
3. It’s ________________(不可能的) to imagine how large the universe is.
4. I am so weak that the doctor told me to ______________(锻炼) more.
5. Sorry, I’m late because my mother’s _________________________(病)。