Final answer:
While most river-valley civilizations had governments led by kings or ruling classes, the Indus Valley Civilization may have been an exception, with little evidence of hereditary monarchs, indicating that option 1 is likely the factor not required for development.
Step-by-step explanation:
The development of the four river-valley civilizations of Mesopotamia, Egypt, the Indus Valley, and China was influenced by several common factors. These include a government run by a king or a ruling class, the division of labor, a location next to rivers, and a surplus of food. All of these factors were crucial in allowing such civilizations to flourish; however, the question which asks about the factor that is NOT a reason for the development of these civilizations can be misconstruing. While a king or a powerful ruling class was typical for many civilizations, the Indus Valley civilization, unlike the others, shows little evidence of political power concentrated in the hands of hereditary monarchs. Instead, it may have developed around a series of small republic-like states, as religious specialists presided over a hierarchical class system. Thus, option 1, suggesting that a government run by a king was essential for the development of all four river-valley civilizations, is not accurate.