Sternly, maybe could just be grim ( formiadable, harsh, uninviting, depressing, lack of humor, etc)
A, the author wants us to introduce us to the character and events that will cause the conflict.
<span>C. She lives on the twentieth floor of an old apartment building somewhere in Manhattan.
This option is accurate since it contains articles and modifiers that are grammatically correct:
i) "the" is used before the word "twentieth" (a noun modified by ordering- i.e. first, second, third, and so on...)
ii) "an" is used before the word "old" (which begins with a vowel)
</span>
