Final answer:
The increasing influence of oil-rich Middle Eastern nations over other countries was due to the abundance of oil resources. The establishment of OPEC demonstrated the region's ability to impact global oil prices and economies heavily reliant on oil imports.
Step-by-step explanation:
The factor that led to the increasing influence of the oil-rich Middle East over other nations is C) Abundance of oil resources. North Africa, Southwest Asia, and Turkestan are regions known for their substantial reserves of oil, natural gas, and minerals. These resources have been the cornerstone for several Middle Eastern countries in gaining wealth and influencing the global economy, particularly through the export of oil. The significance of these oil reserves became particularly apparent with the establishment of the Organization of Petroleum Exporting Countries (OPEC), which has a substantial impact on global oil prices.
The Energy Crisis of the 20th century further demonstrates the importance of the Middle East's oil resources. During this time, OPEC aimed to regulate the oil market and shift the power dynamics to make oil-importing nations dependent on oil-exporting countries. This strategic collective action among oil-producing countries illustrated the geopolitical leverage gained through oil wealth.