"c. The city became a central hub for trade, which contributed to the empires growth" best describes the effect of Constantine moving the capital to Constantinople, since it was a thriving metropolis.
They were usually paid the ransack enemy ships rather than focusing on anyone else, they delivered information to people under the radar as well.
It's the day of great significance in South Africa because of the two wars that they had: The battle of Blood River in 1838 between the voortrekkers and the Zulus.
Hope this helps!
