The correct answer is 2. Efficient agricultural practices made the workforce available for other endeavors.
Before the development of efficient agricultural practices, most people in Egypt worked the entire day in order to produce food and resources for an ever increasing population. But, since the Nile river presented cyclic floodings that left a fertile mud on the riverside, it was taken as an advantage by the Egyptian farmers to make the production more efficient. Understanding these patterns plus the development of agricultural techniques, such as the plow and irrigation practices, considerably increased the production and reduced the quantity of time, resources, and effort applied. This allowed ancient Egyptians to use workforce for other endeavors with political, organizational, scientific, and religious purposes.