Which scenario indicates a fitting is not suitable for direct use with LFNC-B?

The scenario where a fitting marked "LFNC-C" is indicated as unsuitable for direct use with LFNC-B is correct because LFNC-B and LFNC-C represent different classifications of fittings that may have varying specifications, capabilities, or regulations. Standards for fittings are typically established to ensure compatibility, safety, and performance within specific applications.

In this case, a fitting marked "LFNC-C" is not interchangeable with an LFNC-B fitting. Using a fitting designated for a different classification can lead to potential safety issues or system failures, as they may not meet the requirements or parameters necessary for the intended application involving LFNC-B.

Moreover, it is essential to adhere to specific codes and standards when selecting fittings to avoid using components that have not been evaluated or certified for that application, which is why other scenarios may also represent unsuitable options, but they focus on varying aspects like certification and combined markings rather than direct classification compatibility.