Final answer:
Anarchy is the correct antonym for 'stratum' as it represents the absence of a structured social order, in contrast to the organized classification of social levels indicated by a stratum.
Step-by-step explanation:
The antonym for “stratum”, which represents a social class or level of society consisting of people with similar cultural, economic, or educational status, is “anarchy.” This is because anarchy is the absence of any structured social order, contrasting with the organized categorization that a stratum implies. Social stratification refers to a society's categorization of its people into rankings based on factors like wealth, income, education, and power, which is indicative of a structured, orderly society. Thus, the correct answer to the student's question is option b) Anarchy.