How does a conductor confirm the weight of a train's cargo?

Answer: B — By reviewing shipping documents and using scales when necessary

The correct method for a conductor to confirm the weight of a train's cargo is through reviewing shipping documents and using scales when necessary. This approach is crucial as shipping documents provide detailed information about the cargo, including its declared weight. These documents typically include bills of lading or waybills, which outline what is being transported and its corresponding weight. In addition to relying on documents, using scales is essential when there is a need to verify that the actual weight of the cargo matches the shipping documents. Accurately measuring weight is vital for safety and compliance with regulations, as overloading a train can lead to dangerous situations, including potential derailments or damage to the track infrastructure. Other methods mentioned, such as estimating based on the size of the cargo or checking the weight of empty cars, do not provide a reliable or precise measurement of the actual cargo weight. Consulting the train's maintenance log is unrelated to the cargo weight and focuses instead on the upkeep and safety checks of the train itself. This underscores why reviewing shipping documents and utilizing scales is the most effective and reliable method for confirming the weight of a train's cargo.