b and 4..................................................
All nouns (common and proper) name persons, places, things, or ideas. There are differences between them, though.
Common noun: names GENERIC persons, places, things, or ideas (i.e. man, park, planet, religion)
Proper noun: names SPECIFIC persons, places, things or ideas (i.e. Billy, Central Park, Mars, Christianity)
At the dairy factory, the centrifuge separated the cream from the milk.
I hope this helped!