The correct answer is B. Cargo loaded into vehicles and/or containers prior to lifting must be secured before the lift commences. The reasoning is that proper cargo securement is critical for safe crane operations. Unsecured cargo inside vehicles or containers can shift during the lift, which could cause the load to become unstable and potentially lead to a dangerous situation. The other statements are all true - crane operators must adhere to manufacturer's load limits, and all lifting points must be checked prior to the lift for safety.