Task 3. Complete the sentences: 4. Tsiolkovsky proved that rockets needed to have multiple ______.

Analysis: Konstantin Tsiolkovsky is considered the father of astronautics. His theoretical work laid the foundation for rocket propulsion and spaceflight. He recognized the necessity of multi-stage rockets to achieve the velocities required for space travel, especially to overcome Earth's gravity. Therefore, rockets needed to have multiple stages.

Answer: stages