Respuesta :
I'd say the answer is D, protect their cities from enemy invasion. I mean, how could mere pillars protect whole cities from enemies? I wouldn't say they were used for such protective purposes.
Answer:
D. protect their cities from enemy invasion.
Explanation:
Ancient monuments like obelisks and stelae might have religious or historical value for us and for the civilization that made them, but they have no strategical value and make no difference during an invasion or war.