What must be checked regarding the fuel tank cap during inspection?

Answer: B — It must be locked while driving

The requirement that the fuel tank cap must be locked while driving is crucial for safety and efficiency during vehicle operation. A secure fuel tank cap prevents fuel from spilling out while the vehicle is in motion, which can reduce the risk of accidents and environmental contamination. Additionally, a locked fuel cap helps to maintain the correct pressure within the fuel system and can deter fuel theft. Other options present alternatives that do not meet safety standards. For instance, a loose cap could lead to fuel leakage, while a cracked cap would compromise the integrity of the fuel system. The cap's color is irrelevant to its functionality and safety. Thus, ensuring that the fuel tank cap is locked is a vital aspect of the pre-trip inspection process.