Problem: How does the sentence end?

Justin gave their heartfelt congratulations to Christopher after 
Answer: Christopher managed to win a major sports tournament.

Problem: How does the sentence end?

Aaron asked to borrow money from Steven because 
Answer: Steven  remembered to bring their wallet with them.

Problem: How does the sentence end?

The belly button of Christopher has lint in it, while Matthew's has none, so 
Answer: Christopher is the filthier person.

Problem: How does the sentence end?

Justin was a little dwarf compared to Ian because 
Answer:
Justin was so short in stature.