Which word refers to a member of the middle class and is typical of the middle class?

The term "bourgeois" refers to a member of the middle class, particularly in the context of socio-economic discussions. Historically, it is associated with the capitalist middle class that emerged in Europe during the late Middle Ages and the Renaissance. The bourgeoisie is characterized by its ownership of capital and means of production, as well as its prominence in commerce and trade. This word captures the attributes, values, and lifestyle typical of this social class, often connoting traits such as materialism, conventionality, and a focus on social status.

In contrast, the other choices do not pertain to the middle class. "Boisterous" describes someone who is noisy and cheerful, "boorish" refers to someone who is rude or insensitive, and "caustic" characterizes something that is capable of burning or corrosively sarcastic. None of these terms relate specifically to the concept of the middle class, making "bourgeois" the most accurate selection in this context.