What encompasses all components responsible for propelling a rocket?

The correct answer is propulsion systems. Propulsion systems are integral to the rocket's ability to generate thrust, which is necessary for overcoming gravitational forces and achieving lift-off. These systems encompass the engines, fuel, and various mechanisms involved in the combustion process or other types of propulsion, such as electric or nuclear systems. The propulsion system is designed to convert the energy stored in the fuel into kinetic energy, propelling the rocket forward.

The other options, while related to the operation of a rocket, do not directly pertain to the generation of thrust. Control systems are significant for maintaining the stability and trajectory of the rocket during flight. Guidance systems are responsible for navigation and ensuring the rocket follows its intended path. Inertia systems are related to the dynamics of the rocket and its response to forces but do not themselves propel the vehicle. Thus, while all these components are essential for the overall functioning of a rocket, only propulsion systems specifically focus on the thrust necessary for lift-off and movement through space.