As always it depends. If country C requires visa (ahead of travel) for passport holders of country B, but Visa free travel for passport holders of country A, yo

As always it depends. If country C requires visa (ahead of travel) for passport holders of country B, but Visa free travel for passport holders of country A, you can just enter with your country A passport. No problem for country C to know this. But remember the travel ban for Muslim country citizen in the US? There being citizen of B will in all cases prevent you from entering (except, of course you criminally lying plus intelligence agency screwup)