Answer:
1. if- if
2. I- I
3. marathon- she
4. There- there
5. alone- what
6. encore- what
7. What- what
8. damaged- what
9. night- or was it Tuesday- we went to the opera.
10. something- what is it?
Explanation: I wrote the two words that the dash would go in between for each sentence. 9 needs two dashes.