Problem: How does the sentence end?

Lawrence was too sensitive to caffeine, but Kenneth needs it to wake up, so
Answer: Kenneth drinks caffeinated coffee in the morning.

Problem: How does the sentence end?

Kayla dated many more people at once than Betty, because
Answer: Betty was in an open relationship.

Problem: How does the sentence end?

Steven was very good at writing fiction while Ryan was not, so
Answer: Steven taught a class on how to write fiction.

Problem: How does the sentence end?

Kevin used a knife to trim his fingernails while Christopher buffed with an emory board.
Answer:
Christopher was more careful.