Problem: How does the sentence end?

Amy loved being around people but Maria found it exhausting, so 
Answer: Amy went to the party alone.

Problem: How does the sentence end?

We had abundant money in the summer but were always broke in the winter , since the 
Answer: winter was when we spent more.

Problem: How does the sentence end?

At the end of the year, Christine realized why she failed while Mary got A's; 
Answer: Christine failed to resist play over studying.

Problem: How does the sentence end?

Rebecca was under the car changing the oil while Laura watched, since 
Answer:
Rebecca was handy with cars.