A social structure defines how a civilization is organized, not the specific details like taxes, records, or government treatment. The correct option is a).
Social structure refers to the way a society is organized, encompassing the different social levels, roles, and relationships within the community. While the other options might be influenced by the social structure, they are not the definition of it itself.
b) how many taxes a king collects from enslaved people: This is a specific aspect of the economic system within the social structure.
c) the way scribes record social events: This is a function performed by a particular social group within the structure.
d) how the government treats the lower classes: This describes the interaction between different levels of the social structure.
Therefore, only a) the way a civilization is organized captures the overarching concept of social structure, encompassing all the other aspects mentioned.
The answer is a) the way a civilization is organized.