Based on the context of the passage above, a shibboleth is a belief of classesof people. Option B is correct.
A shibboleth refers to any custom or tradition, a phrasing or a single word, that characterizes one particular group of people and distinguishes it from another group of pleople. Shibboleths have been implemented in many societies as passwords, forms of self-identification, conveying loyalty and affinity, keeping traditional segregation, or protecting from real threats.