Which two parts of the batteries must be checked before operation?

The correct answer focuses on the importance of ensuring that all electrical connections related to the batteries are secure and functioning properly before operating the vehicle. Checking the connections is crucial because loose or corroded connections can lead to electrical failures, which may cause the vehicle to malfunction or even become inoperable. Ensuring that the connections are tight and free of corrosion significantly enhances the reliability and safety of the vehicle's electrical system.

While other factors such as battery fluid level and cable damage are also important for overall battery maintenance, the immediate operational readiness is best assessed through the integrity of the connections. Without secure connections, the vehicle cannot properly draw power from the batteries, leading to potential operational issues. This routine check is a standard part of vehicle safety protocols to prevent unexpected failures during operation.