I would say mostly economic factors: common currency, common market, wide-scale trade among the countries. If one country is hit, the others will also suffer: this brings in the feeling of solidarity.
other than that, European culture is actually quite unified, with many shared valued, such as universal health care and religious freedom, yet connection to Christianity.
B. The Ohio River Valley was near the coast and offered trade opportunities.
Answer: chief of which is a gradual decrease in the fertility and hence the productivity of Egypt’s riverside agricultural lands
Explanation:
Refuse to obey laws that are unfair and unjust to all citizens