Answer:
C: Who are you waiting for?
Step-by-step explanation:
Preposition means "placing before." The traditional or classical rule requires that prepositions should not end sentences. However, following the trend of modern usage, it is now accepted as a colloquial form. So it is possible to move the preposition to the end of the sentence in questions beginning with a preposition + whom : For whom are you waiting ?/ Who are you waitin for ?