I just cleaned the trashcan and not the driveway, so the 
OPTIONS:
- trashcan was a lot cleaner.
- driveway was a lot cleaner.
trashcan was a lot cleaner.

She wanted a fountain pen but bought a rollerball pen instead, because the 
OPTIONS:
- fountain pen is more expensive.
- rollerball pen is more expensive.
fountain pen is more expensive.

The pregnancy was the responsibility of Christopher but not Kenneth, because 
OPTIONS:
- Christopher was in a relationship with the woman.
- Kenneth was in a relationship with the woman.
Christopher was in a relationship with the woman.