Answer:
B. meetinghouse
Step-by-step explanation:
Although nothing is in bold here, I'm assuming that this refers to the pronoun "its".
Pronouns are used to replace nouns or phrases previously mentioned in order to avoid repetition.
Here, basically, we have a voice announcing somewhere in the meeting house which silenced the din that filled meetinghouse's cavernous hall.
So now, looking at the full sentence, we can see that the pronoun "its" replaced the noun "meetinghouse".
The noun replaced with pronoun is called that pronoun's antecedent.