Which of the following ingredients is commonly added to chocolate sauce for creaminess?

Evaporated milk is commonly added to chocolate sauce to enhance its creaminess. This ingredient contributes a rich, smooth texture due to its higher fat content compared to regular milk. The process of evaporation removes water, concentrating the creaminess and flavor of the milk, making it ideal for creating a luscious chocolate sauce. The additional fat from evaporated milk not only provides a velvety mouthfeel but also helps to balance the sweetness of the chocolate, resulting in a more rounded flavor profile.

In contrast, powdered sugar is primarily used to add sweetness and may alter the texture, but it does not provide the creaminess that evaporated milk does. Flour is generally used as a thickening agent rather than to enhance creaminess and might create an undesirable texture if used in a chocolate sauce. Cocoa powder, while essential for the chocolate flavor, also does not contribute to a creamy texture; it is rather a dry ingredient that adds depth in taste. Thus, evaporated milk stands out as the best choice for achieving the desired creaminess in chocolate sauce.