A. Gandhara civilization
B. Indus Valley civilization
C. Greek civilization
D. Persian civilization

Around 500 B.C., the city of Taxila was the center of Gandhara civilization, which was a hub of Buddhism, learning, and culture:

The correct answer to the question: "In about 500 B.C., the city of Taxila was the center of:__________?" is "Gandhara civilization".