Problem: How does the sentence end?

The book took longer to read than the novella because the 
Answer: novella was much shorter.

Problem: How does the sentence end?

The record store sold more CDs than vinyl records because 
Answer: record players were much less common.

Problem: How does the sentence end?

William got lost in thought more often than Jason because 
Answer: William was prone to daydreaming.

Problem: How does the sentence end?

Jennifer followed the instructions given to them by Megan, since 
Answer:
Jennifer was the natural subordinate.