Which type of sauce is classified as a "mother sauce"?

Béchamel sauce is classified as a "mother sauce" because it is one of the five foundational sauces in classic French cuisine from which numerous derivative sauces can be created. It is made from a basic mixture of milk, butter, and flour, and serves as the base for sauces such as cheese sauce, cream sauce, and others.

The term "mother sauce" refers to those sauces that provide a starting point for the creation of other sauces, offering versatility and serving as building blocks for complex flavor profiles in a variety of dishes. Béchamel is recognized for its creamy, smooth texture, making it ideal for enriching many dishes from gratins to pasta sauces.

The other options, while they may be important sauces in their own right, do not fall under the classification of mother sauces in classical cooking techniques. Marinara sauce is a tomato-based sauce primarily used in Italian cuisine, barbecue sauce is a condiment for grilled meats, and hollandaise, while a mother sauce itself, is distinct from Béchamel in its preparation and ingredients. Hence, Béchamel remains a quintessential example of a mother sauce.