The Smith family made several good investments, and now they no longer struggle to pay for groceries. They do not want to tell people about how much
money they have. Instead they show their financial success by buying
expensive jewelry and a house that has more bedrooms than they actually
need. Their purchases are examples of:
O A. conspicuous consumption.
B. ascribed social standing.
O C. biological characteristics.
O D. gender differentiation.

A: Conspicuous Consumption

Explanation:

This is an example of conspicuous consumption because it is almost exactly correlates with the definition and makes a lot more sense than the other answers.

Here is Wikipedia's definition of Conspicuous Consumption: Conspicuous consumption is the spending of money on and the acquiring of luxury goods and services to publicly display economic power of the income or of the accumulated wealth of the buyer. To the conspicuous consumer, such a public display of discretionary economic power is a means of either attaining or maintaining a given social status.[1][2]

Doesn't that sound a lot like the Smith family that is mentioned in the question?

what is the tax base for the sales tax?

it should be (usually ) 6%