The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
The factor that most promoted the spread of ideas and products from the ancient river valley civilization of Egypt and Mesopotamia to the Greek and Roman, was trade relationships.
Trade was of the utmost importance for these civilizations because it gave them the resources to live and prosper (years later, the money or currency). Through trade, not only goods were exchanged but ideas, traditions, culture, belief systems, stories, and language. One of the best examples of this is the Pantheon of gods that started with the Sumerians in Mesopotamia, which is very alike to the Pantheon of gods of Ancient Egypt, the Indus Valley Civilization, the Greek Pantheon, and the Roman Pantheon. All of them, very similar.
