Read the excerpt below and answer the question. but time drives flocks from field to fold; when rivers rage and rocks grow cold; and philomel becometh dumb; the rest complains of cares to come. (“the nymph’s reply to the shepherd”; lines 5-8) which uses an auditory (sound) appeal to support the idea that natural landscapes are not idealized settings? a“… drives flocks from field to fold; ” b“… rocks grow cold; ” c“… cares to come.” d“philomel becometh dumb; ”

The answer is D) “Philomel becometh dumb". 
Two key pieces of information are needed to correctly answer the question: 
1) Remember that "dumb" also means, and long ago more commonly meant, unable to speak, or mute.
2) Philomel is a princess in Greek Mythology who is raped by her sister's husband and is transformed to a nightingale, a songbird whose song is generally seen as sorrowful. 

Philomel becoming dumb means the princess, transformed into a nightingale, has lost her ability to fill the air with her sorrowful song, her one expression of sadness that she has. This is what makes it an auditory appeal.