Final answer:
The correct tenses are 'came' in the simple past and 'was trying' in the past continuous, showing the actions completed and ongoing at that past moment respectively.
Step-by-step explanation:
The student's question involves choosing the appropriate verb tenses for the given sentences. The correct tenses are based on the context provided by the sentences. When the student came out of the library, the action was completed at a specific point in the past, therefore, the simple past tense 'came' should be used. At that moment, the strange guy was in the middle of an action, so the past continuous tense 'was trying' is needed to show the ongoing attempt to break into the car.
The completed sentence reads: "You won't believe what happened yesterday. When I came out of the library, a strange guy was trying to break into my car!" This demonstrates a clear and consistent use of verb tense consistency.