What type of document reports flaws in software that can affect its performance?

The correct choice is a defect report, as this type of document specifically focuses on capturing and detailing flaws or defects found in the software during testing. A defect report provides a comprehensive overview of the issue, including its potential impact on software performance, reproduction steps, assigned severity, and status of the defect.

The primary purpose of this document is to ensure that defects are logged systematically so that they can be addressed by the development team, ultimately improving the quality and performance of the software. It acts as a communication tool between testers and developers and plays a critical role in the software development life cycle, facilitating the resolution of performance-impacting flaws.

Other document types, like the test case document, are designed to outline test scenarios and expected outcomes for specific functionalities rather than report on defects. Requirements specification outlines the expected features and functions of the software, while an issue log may track a variety of problems encountered during the project, including non-defect related issues that do not necessarily pertain to software performance.