Which of the following represents a valid comment in Python?

In Python, comments are created using the hash symbol (#). When this symbol precedes text, everything following it on that line is treated as a comment and is ignored by the Python interpreter during execution. This is useful for adding notes or explanations within the code to ensure that others, or even the original programmer at a later time, can understand the purpose or functionality of certain code segments.

The correct representation of a comment in Python is the choice that starts with the hash symbol followed by the text of the comment. Therefore, # This is a comment is the valid format that will be recognized as a comment in Python code.

The other formats listed do not conform to Python syntax for comments. For instance, the percentage symbol and double forward slashes are used in other programming languages for comments but are not valid in Python. Similarly, the block comment style represented with the asterisks is also not applicable in Python; although strings can be enclosed in triple quotes for multi-line comments, they are not technically comments as they do not use a specific comment syntax.