Final answer:
Blackbox testing is synonymous with Functional Testing, as it focuses on evaluating a software application's external behavior without knowing its internal structure. It is different from stress testing and glassbox testing, which are concerned with performance under extreme conditions and internal code structure, respectively.
Step-by-step explanation:
Blackbox testing is a method of software testing that examines the functionality of an application without peering into its internal structures or workings. This technique treats the software as a black box, with no knowledge of internal implementation.
The correct answer to the question "Blackbox testing is also known as:" is A) Functional Testing. Blackbox testing focuses on input and output of software applications and is contrasted with whitebox or structural testing, which involves looking at the internal structure of the code.
Stress Testing and Glassbox Testing, also known as whitebox testing, are not synonymous with blackbox testing. Stress testing assesses the system's performance under extreme conditions, while glassbox testing involves understanding the system's internals.