In "Ode on a Grecian Urn", what does the speaker begin to wonder about in lines 35–36 upon seeing the sacrificial procession?
AWhat instrument the musicians are playing, and what song they are playing
BWhich town—by river, coast, or mountain—has been left empty by the people in the procession
CWho the people in the procession are, and why they are dressed in their finest clothes
DWhether the urn itself was created to commemorate this very procession