Answer:
The sentence that contains a preposition is C. Thomas Edison gazed at the bulb.
Explanation:
A preposition is a word used to link words or phrases within a sentence, usually by heading a prepositional phrase in front of nouns. In this sentence, the preposition is the word at that expresses the relation within gazed and the bulb.
*Sentence D also contains a preposition. However, it is not functioning as a preposition itself but as part of a phrasal verb. *
