Why does the author include the last sentence of this excerpt?

a)
to demonstrate carrie's poor judgment

b)
to express a realization that carrie has

c)
to illustrate the mercurial nature of carrie

d)
to hint at the question that will nag at carrie's thought

First things first, I'm not entirely sure what excerpt considering you didn't put any above. So I do not know what the story is.

But I believe that the answer would be..

B. To Express a Realization that Carrie Has

Once again, I cannot answer this question with full sincerity because I do not have the excerpt.

I do hope this helps though! :)

you so ! < 3