Answer:
1. We went to bed early but we could not sleep.
2. I will give you more cookies if you eat the cookies that I gave you earlier.
3. The girl is reading while the boy is eating sweet mangoes.
4. She lost her key's so she can't open her new house.
5. Peter want to be an astronaut because he love's science.
Answer: regressing
Explanation: if a person degenerates, they are losing capabilities and their qualities are decreasing or declining. Basically things are getting worse.
Regressing is returning to an older, less developed state while progressing is getting better.
Degenerating and regressing are going backward while progressing is going forward.
A shadow because there no bird that you can see
Answer:
I think it's formal I always write them that way, so I would say formal.