I'd say A is definitely the correct answer, but also C could be, if the Valley is a place, I really don't know if it is.
Answer:
It forces her to have to outwit her suitors instead of having the option to merely refuse them.
Explanation:
The repetition of the word knock, first of all, conveys a specific literary device which is called Alliteration. Here is the definition of alliteration: It is the appearing of the same, exact letter or sound at the starting point of adjacent or closely linked words. Secondly, the repetitious sound of knocking , conveys the knocking as continuous. Hope that this answers your question.