How much do u think my art s worth a piece???

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

Iam not 100% sure but i believe the term you are looking for is  plein air.