Here is a website that will help you find the answer and understand the poem as well...
http://www.sparknotes.com/poetry/hopkins/section4.rhtml
If you do not wish to visit the site I believe the answer is A.
Because she is mourning her own mortality, because man is mortal.
Explanation:
OA) after the note-taking process
<span>Hey There!
My family and I live under a roof.</span>
The correct answer of the given question above would be option C. The sentence in which the prepositional phrase best modifies the verb saw is: through the window, I saw the bird flying. The prepositional phrase of this sentence is "through the window" with the preposition "through" and this modifies the verb "saw".