Explanation: Graybox testing is a combination of whitebox testing and blackbox testing. In graybox testing, the test engineer is equipped with the knowledge of system and designs test cases or test data based on system knowledge. The security tester typically performs graybox testing to find vulnerabilities in software and network system. Answer: C is incorrect. Whitebox testing is a testing technique in which an organization provides full knowledge about the infrastructure to the testing team. The information, provided by the organization, often includes network diagrams, source codes, and IP addressing information of the infrastructure to be tested. Answer: A is incorrect. Integration testing is a logical extension of unit testing. It is performed to identify the problems that occur when two or more units are combined into a component. During integration testing, a developer combines two units that have already been tested into a component, and tests the interface between the two units. Although integration testing can be performed in various ways, the following three approaches are generally used: The top-down approach The bottom-up approach The umbrella approach Answer: B is incorrect. Regression testing can be performed any time when a program needs to be modified either to add a feature or to fix an error. It is a process of repeating Unit testing and Integration testing whenever existing tests need to be performed again along with the new tests. Regression testing is performed to ensure that no existing errors reappear, and no new errors are introduced.