Problem: How does the sentence end?

The doctor was able to diagnose the reason for the man's cough, but not his headache. The reason for the
Answer: headache was mysterious.

Problem: How does the sentence end?

Brian finished cleaning a closet in the bedroom before Kyle because
Answer: Kyle was a very messy person.

Problem: How does the sentence end?

The muffins in Michaels oven were almost ready when Ian showed up, so
Answer: Ian asked for one.

Problem: How does the sentence end?

Randy was making Michael body armor for a costume even though
Answer:
Randy had never made it before.