Solution:
The task is to choose the correct meaning for the underlined phrasal verb 'petered out' in the given sentence.
- The sentence is: "The fighting which started in the night had petered out by morning."
- The phrasal verb 'peter out' means to gradually diminish, lessen, or stop.
- In the context of the sentence, 'petered out' signifies that the fighting gradually ceased or died down by morning.
Answer: had petered out