Let's define the terms related to software development:
(A) The process of writing code is called coding or implementation.
(B) Running a program is called execution. Testing is the process of running a program to find issues.
(C) Adding new features is part of development or maintenance.
(D) Debugging is the specific, methodical process of finding the root cause of an identified error (a bug) in the software and then correcting it. It is a reactive process that follows the discovery of a bug during testing or use.
Therefore, the best description of debugging is identifying and fixing errors.