Concept:The main reason for building more hydro-electric power projects is to satisfy rising electricity demand.Explanation:The population and economy of developing countries are growing rapidly.This creates an ever increasing demand for power for homes, industries, and businesses.Hydro-electric power is a renewable and affordable source of energy that can help meet this growing need.Rainfall and waterfalls may provide suitable conditions, but they are not the main reason for constructing more projects.Answer:B. There is ever increasing demand for power