Black Box Testing is called so because it symbolizes testing without any knowledge of the software's internal structure, just like a tester is working with a "black box" and doesn't need to see what's inside. This approach emphasizes testing solely based on external behavior.

A primary key in a database table is used to uniquely identify each row in the table. It ensures that no two rows have the same values for the primary key, making it a crucial concept for data integrity and efficient data retrieval.

In this scenario, the issue is related to validation. Verification ensures that the software is built as per the specified requirements, while validation ensures it fulfills user needs. The problem arises because the software may meet its documented requirements but not satisfy what users truly need in the real world. This highlights the importance of both verification and validation in the software development process.

The primary purpose of using an API in software development is to enable interoperability between different software components. APIs facilitate communication and data exchange between applications, allowing them to work together.

System testing focuses on validating the entire software system, ensuring that it meets the specified requirements and functions as intended. This includes verifying the software architecture, interfaces, and overall functionality.

Adherence to ISO/IEC 25010 ensures software product quality by defining and measuring quality attributes. It provides a framework for assessing and improving various software quality characteristics, including functionality, reliability, performance, and more, thus contributing to overall product quality.

Security is a critical quality attribute that pertains to the software's ability to safeguard against unauthorized access and data breaches. Security measures are implemented to protect sensitive information and ensure that only authorized users can access the system.

API stands for "Application Programming Interface." It is a set of rules and protocols that allow different software applications to communicate with each other. APIs define how software components should interact.

The "undo" heuristic in UI design is about providing users with the ability to reverse their actions. This feature adds a sense of control and safety for users, allowing them to correct mistakes or change their course of action.

System testing is positioned at the level where the entire software system is tested to ensure its correctness and functionality. It typically follows unit testing and integration testing, coming before acceptance testing in the testing life cycle.