Which of the following is an example of debugging?

The choice indicating that a developer finds and fixes a defect exemplifies debugging because debugging specifically refers to the process of identifying, isolating, and correcting defects or issues in the code. This involves systematically investigating the code to determine what went wrong and making necessary changes to resolve the issue.

In this context, the act of finding a defect is the initial discovery stage of debugging, while fixing it is the action that completes the debugging process. Debugging often requires a deep understanding of the system and its behavior, allowing the developer to not only address the identified defect but also verify that the fix does not introduce new issues.

The other activities mentioned do involve important aspects of the software development and testing process, but they do not fully represent debugging. For example, reporting a defect is part of the testing phase, while retesting a fix primarily focuses on verifying that the solution works correctly rather than the process of isolating and fixing the defect. Unit testing, on the other hand, is a quality assurance process that might not always involve debugging unless defects are found during that testing phase.