Answer:
C, third sentence
Explanation:
C is the only sentence that contains 2 adjectives (sudden/hard) which precede and describe the same noun (storm).
The comma is used incorrectly in regards to sentence A and sentence D because a comma cannot be put between an adjective and a noun.
Not only that, 'six' and 'one' from sentence A might not even classify as adjectives here; they are numbers preceding a noun and some say they serve as 'determiners'.
Its usage in sentence B is correct (it's an apposition), but the question wants you to identify the comma in relation to the coordinating adjectives, thus leaving you with option C because, in this case, the comma separates 2 adjectives.
