Final answer:
A frictionless pendulum and a mass on a spring in a vacuum are considered closed systems because they are idealized to not exchange matter with their surroundings and are assumed to have no energy loss due to friction or resistance.
Step-by-step explanation:
The question is asking which of the given options represents a closed system. A closed system is defined in physics as a system that allows energy transfer but does not allow matter to enter or leave. The Earth is not a closed system because it receives energy from the Sun and cosmic rays, and can lose matter into space. A car is not a closed system; it needs fuel to operate and emits exhaust gases. A frictionless pendulum, while it is an idealized concept, can be considered a closed system for the purposes of studying physics because it assumes no energy loss to the surroundings. Lastly, a mass on a spring in a vacuum is also considered a closed system since there is no air resistance or other form of friction that would allow energy to leave the system.