The correct answer to the question "Who developed the use of liquid fuel for rockets?" is:
2. Robert Goddard
Robert Goddard is the individual credited with developing the use of liquid fuel for rockets. He is often referred to as the "father of modern rocketry" due to his pioneering work in this field. Goddard's experiments and research laid the foundation for the development of liquid-fueled rockets, which have been essential for space exploration and technological advancements in rocketry. His work was crucial in shaping the future of space travel and rocket propulsion.
