Who is depicted in the image below?

The answer is

What i think is that it adds loudness for preachers/church choirs. it is also able to hold up a lot of weight without pillars. : )) idek tho

There's videos on the internet

The options for this question is 
a.) a private building used for religious purposes
b.) a stadium used for athletic events, chariot racing, and acrobatics
c.) a central building surrounded by religious and governmental buildings
d.) an open space in a town used as a central gathering place or event