Answer:
The underlined portion of the sentence is an:
C. adverbial phrase.
Explanation:
We must be careful not to be fooled by the use of "before". In the context and manner it is used here, "before" is a synonym for "in front of". It is heading the phrase that modifies the verb "brought", and it is indicating a place. Therefore, we are talking of an adverb of place. The whole phrase functions as an adverb, indicating to where Charles Darnay would be brought. We have, thus, an adverbial phrase.
