the answer is A!!!......................
Through multiple revolutions people have adapted to and affected their environments. As civilizations settled, new advances in agriculture and tools were made to allow for a less-nomadic society. Through advances such as iron tools and food stock, civilizations settled creating the basis for large empires to come later. Also through the innovation of weapons and armor, empires were able to better control and defend larger territory allowing for exponential expansion. Finally, with new advances made by different civilizations, trade increased as demand for new products from other empires grew.
The alliances system meant that a local conflict could easily result into an intimidating global one. The overall cause of World War was the assassination of Archduke Franz Ferdinand. Nationalism was a great cause of World War one because of countries being greedy and not negotiating.
Your welcome I don't know if that helped. But yea.
I would say either A or D, hope I helped, sorry if I didn't!!!