Final answer:
The misspelled irregular plural noun is 'oxens'.
Step-by-step explanation:
The misspelled irregular plural noun in the given options is oxens. The correct plural form of 'ox' is 'oxen', not 'oxens'.
Deer, sheep, and teeth are all spelled correctly and are irregular plural nouns. 'Deer' is both singular and plural, 'sheep' is both singular and plural, and 'teeth' is the plural form of 'tooth'.
So, the incorrect plural noun is oxens.
Learn more about irregular plural nouns