Colonies , protectorates , spheres of influence
The answer is A, natural selection.
The transcontinential railroad brought more money to the railroad companies because more people had access to the railroads, therefor using them more, and money was brought in. Not 100% sure, but that is my guess
The final fall of the Byzantine Empire was caused by attacks from the Ottomans.
The Byzantine Empire fell, and Islam spread into Eastern Europe. The Byzantine Empire fell in 1453. The main reason of its fall was a significant number of attacks made by the Ottoman Turks. In 1454, Constantinople finally surrendered to them.
Christopher Columbus came to America (he did not find it.) with the boats Nina, Pinta, and the Santa Maria.
