Problem: How does the sentence end?

The girl put the history book back on the shelf and read the magazine because the
Answer: book was boring.

Problem: How does the sentence end?

Ian had a beautiful aquarium full of fish but Michael did not because
Answer: Ian loved collecting exotic fish.

Problem: How does the sentence end?

Jeffrey had more followers on Instagram than Christopher had, because
Answer: Christopher was a less attractive person.

Problem: How does the sentence end?

Mary has bad dandruff, but Cynthia has never had that issue.
Answer:
Mary lives in a dryer climate.