The dog bit it's master. I did'nt stop. The dog bit its master. I didn't stop. Improper Possessive Proper Nouns Pluralised common nouns must not have an 's' to denote the possessive case.
Proper nouns require the 's'.
The problem is ill understood. The problem is ill-understood. It is incorrect to end a sentence with a preposition. I know where he is at. I know where he is from.