What is the role of live contact shoes on a car?

The role of live contact shoes on a car primarily involves connecting power to the train, enabling it to draw electrical energy from an overhead source. These shoes conduct electricity from the overhead wire to the train's electrical systems, allowing operations such as propulsion and onboard systems to function effectively.

Additionally, live contact shoes can also play a role in providing grounding. This is crucial for safety, as it helps to prevent electrical faults that could lead to dangerous situations, ensuring that the train operates safely on its track.

While controlling air supply is not a primary function of live contact shoes, the interaction between electrical and pneumatic systems is vital in the overall operation of trains. Therefore, the inclusion of options that encompass power connection and grounding underlines the comprehensive role of live contact shoes in train operations, justifying the correct answer as encompassing all of these aspects.