Which of the following is true regarding live contact shoes on a car?

The statement that all cars are equipped with live contact shoes is accurate. Live contact shoes, which ensure the train receives the necessary electrical power for operation, are typically standard equipment on all passenger cars in a rail system. This design enhances overall safety and operational efficiency, as every car is expected to maintain a consistent electrical connection throughout the train’s length during travel.

When considering the other options, stating that only some cars are equipped with live contact shoes does not reflect the uniform application of these components across all train cars, as they are essential for the electrical system's functionality. The notion that live contact shoes are only used in emergencies is also incorrect, as they are a core part of the train's operational capability and are not reserved for emergency situations. Lastly, mentioning that live contact shoes are optional for engineers misrepresents their standardized role; they are a required feature rather than an optional one. Therefore, recognizing that all cars are equipped with live contact shoes clearly supports the understanding of their essential functionality within train operations.