D because a metaphore compares someone or something to something else to add some understanding or to just to help you have more interesting writing (hope that helps)
The right answer is d. she is a gem. Metaphor is an imaginative way of describing something by referring to something else that has the qualities that you want to express. In this case, the narrator wants to describe that the woman is valuable, maybe for her morals or her beauty, in order to use the metaphor, he compares her with a gem. Gems are high valuable stones.
