Which statement best describes regression testing?

Regression testing is primarily concerned with ensuring that recent changes to the codebase, such as enhancements, bug fixes, or new functionality, have not inadvertently introduced new defects into existing features. The purpose is to confirm that the existing software continues to perform as expected after updates are made. This is vital because even minor alterations can have unforeseen consequences on previously functioning components.

While other statements touch on important aspects of software testing, they do not specifically address the focus of regression testing. Ensuring all features function as intended is more aligned with the scope of functional testing, compliance with industry standards pertains to validation against specific regulations or benchmarks, and user acceptance testing focuses on end-user satisfaction with new features rather than confirming that existing functionalities remain unaffected. Therefore, the first choice accurately encapsulates the essence of regression testing.