we replaced the bed with a mattress because space was limited in the bedroom, the
OPTIONS:
- mattress was vast.
- bed was vast.
bed was vast.

Joel preferred to drive when Christopher was in the car, since
OPTIONS:
- Joel was a very steady driver.
- Christopher was a very steady driver.
Joel was a very steady driver.

Of the two, Robert is less intelligent than Brian is. That's because
OPTIONS:
- Robert went to and completed college.
- Brian went to and completed college.
Brian went to and completed college.