Answer:
Sentence 2: The dogs were enjoying their bones.
Step-by-step explanation:
Sentence fragments are incomplete sentences that were disconnected from the main clause by a period. There is a way to connect them back and is by changing the period with another punctuation as a comma.
The option above is a clear sentence fragment because there is a lack of context about what was happening by the time the dogs were enjoying their bones.
I hope this answer helps you.