What is an opaque expression in programming?

An opaque expression in programming refers to a construct that does not reveal its underlying implementation or behavior. This means that the expression is abstracted away from the programmer, making it complex for a developer to understand what it precisely does just by looking at it. The correct answer draws attention to the specific statements or behaviors that exist within programming languages without necessarily detailing their internal workings.

In programming, opaque expressions can serve various purposes, such as encapsulating complex logic or providing a simplified way to perform operations without exposing the underlying complexity. This can improve code readability and maintainability, as it allows developers to focus on high-level operations rather than getting bogged down in intricate details.

The other options outline concepts that are either broader or misaligned with the notion of "opaque expressions." While comments in code can serve to clarify the implementation, they do not contribute to the meaning or function of the code itself. Performance optimization methods pertain to enhancing the efficiency of a program but do not directly relate to the opacity of expressions. Lastly, error-handling mechanisms are designed to manage errors and exceptions in code, rather than defining expressions without revealing their inner workings. Thus, the focus on specific statements of behaviors aligns most accurately with the definition of opaque expressions in programming.