Which of the following is NOT a compiled programming language?

The correct answer identifies CSS as not being a compiled programming language. CSS, or Cascading Style Sheets, is a style sheet language used for describing the presentation of a document written in HTML or XML. It is primarily used for layout, design, and visual appearance rather than implementing logic or algorithms, which is characteristic of compiled languages.

In contrast, C++, Java, and Assembly are considered compiled languages. They are designed for more complex programming tasks and require a compiler to transform the source code written by the developer into machine code that can be executed by a computer. C++ and Assembly are typically compiled to target specific hardware architectures, while Java is compiled to bytecode that runs on the Java Virtual Machine, which allows for platform independence.

Thus, CSS stands apart in this context, as it does not undergo a compilation process nor is it used for creating executable programs, clearly marking it as the correct option in the question.