"Jonas was beginning to be frightened is an independent clause
There aren't any prepositional phrases
Compound sentence
It adds to the overall effect on the readers because it shows that Jonas is uncertain and makes the readers realize the correction that Jonas makes to make the sentence more reasonable.
Courage is a virtue seems like the answer, but I haven’t read the book. Though, I’m making an education guess because it takes courage to go to the moon.
This is true. It is proper to wait for intermission to enter because entering beforehand could cause disruption and distraction from the concert which is considered very rude.