What is a key reason to include metaphors in a literary work

In this unit we learned about arguments and

The book the sweet-hereafter; in section four, which of the following is the extended metaphor for nichole's mental state. a) the room her father built her from the sun-room b) the wheel chair she sits in c)the computer from mr. stephens d) the teddy bear from her childhood

Was chris mccandless a hero why or why not