Answer:
B.) Adverb clause
Explanation:
The given sentence exemplifies a complex sentence where the introductory coma marks the end of a subordinate clause which is beginning with a subordinate conjunction 'since'. The introductory comma after the subordinate clause is employed to shift the transition from adverb clause to main clause. The adverb clause consisting of a subject "our visit" and a verb "visit" functioning as an adverb in the sentence and modifying the verb 'visit'. Thus, the introductory coma marks the transition from the adverb clause to the principal clause and hence, the answer is option B.
