What does system level testing verify?

System level testing focuses on verifying that the complete integrated system functions as intended. This phase of testing is crucial in determining whether the software product is trustworthy and operates correctly in its environment. It encompasses a range of considerations, including functionality, performance, and security, ensuring that the software meets requirements and can handle expected workloads without issues.

This level of testing involves assessing not just individual components but also how they interact and behave as a group, which is critical for establishing the overall reliability and integrity of the system. Trustworthiness incorporates both functional and non-functional assessments, which are paramount for user confidence and compliance with standards.

The other options misinterpret the focus and scope of system level testing. While internal controls, physical interfaces, and individual unit testing are important, they represent different levels or areas of assessment that do not wholly encapsulate the purpose of system level testing. The overarching goal is to validate the complete product's reliability and effectiveness in a real-world setting, which is why the correct answer emphasizes the trustworthiness of the software product.