Which words in this sentence are common nouns?
during montezuma's rule, the aztec empire stretched from ocean to ocean.

Common nouns are type of nouns which are not particular or specific in a certain subject –person, place, thing, event or an idea. In the sentence we can identify the commons nouns which are:
 1.          Rule – if we take out the proper noun of Montezuma, whose rule is it? Then which is now a common noun
2.          Empire – if we also examine empire without the Aztec, whose empire is it? Very broad and unspecified.
3.          Ocean – here is the most obvious of the common nouns in the sentence “ocean to ocean”. Which ocean specifically?

What is the assignment?