What begins a single-line comment in programming?

In programming, a single-line comment is typically initiated using two slashes (//). This syntax is widely utilized in languages such as C, C++, Java, and JavaScript. When the compiler or interpreter encounters these two slashes, it recognizes that everything following them on that line should be ignored during the execution of the code. This allows programmers to add notes or explanations without affecting the functionality of the code.

While the other options do represent comment syntax in different programming contexts, they are not universally applicable for single-line comments across the majority of programming languages. For instance, some languages like Python and Ruby use a hash symbol (#) for comments, but this does not apply to all scenarios or languages as effectively as the double slashes do. Understanding the syntax for comments is essential for clear documentation in the programming process, aiding both the author and others who may read or work with the code later.