Problem: How does the sentence end?

Ian had a very nocturnal schedule but Derrick was a morning person. 
Answer: Derrick never slept until noon.

Problem: How does the sentence end?

Brett did all the speaking for William in public, because 
Answer: William had an introverted personality.

Problem: How does the sentence end?

The violets in the garden of Natalie grew much shorter than Rebecca's because 
Answer: Rebecca is great at gardening.

Problem: How does the sentence end?

Depression is the main cause of Angela's visit to Tanya, so 
Answer:
Angela is likely a client.