Define the Mighty “It”

1. It is raining.
2. It looks like a nice day.
3. It was a dark and stormy night.
4. It made me angry.
5. It was three in the morning.
6. It felt like doom.
7. It is hot in here.
8. It turns out she was his wife.
9. It happens to be true.
10. It is time to quit.