Read the following sentence and find out the subject nouns in them.
Hannah should have avoided doing this.

The correct answer is: Hannah

A subject noun is a noun that is the subject of the sentence. A subject is a noun that performs the action in that sentence. In contrast, an object noun is a noun that is the object of the sentence i.e., the object noun is the receiver of the action. 'Hannah should have avoided doing this', here the subject noun is 'Hannah'.