I believe that the answer to the question is B.
When Germany attacked France through Belgium. within hours, Britain declared war on Germany
The answer would be the geography of the country. Its mountain terrain and bodies of water created a boundary to each city-state. Each city-state created their own society. For example, Sparta had created a military society while Athens is the center of many intelligent people. Each city-state also has their worshipped specific gods, Aside from Zeus, Poseidon, and Hades.
