Which of the following best describes the source code?

The best description of source code is human-readable instructions for programming. Source code is written in programming languages that are designed to be understandable by humans, allowing developers to write algorithms and logic that can later be translated into machine code or compiled into an executable program. This human-readable format is essential because it enables programmers to communicate their ideas and solutions effectively, as well as to collaborate and maintain the code over time.

In contrast, other options do not accurately capture the essence of source code. For instance, executable commands understood by a computer refer to machine code or binaries that the computer can run but are not human-readable, thus not representing source code itself. Similarly, a written script that requires no transformations might imply that the code is already in a format the machine can understand, which is not true for most source code. Finally, a graphical representation of the coding environment pertains to integrated development environments (IDEs) or visual tools rather than the actual source code being written.