To answer this question, you need to understand the concept of functional testing.
Functional testing is a type of software testing that checks whether the software system meets the specified functional requirements. It focuses on testing the individual functions or features of the software to ensure that they work correctly.
Let's go through each option to understand why it is correct or incorrect:
Option A) Boundary value analysis - This option is correct because boundary value analysis is a form of functional testing. It involves selecting test cases that are at the boundaries of the input domain, such as the minimum and maximum values, to check if the software functions correctly at these boundaries.
Option B) Usability testing - This option is incorrect because usability testing is not a form of functional testing. Usability testing focuses on evaluating the user-friendliness and ease of use of the software, rather than testing its individual functions.
Option C) Performance testing - This option is incorrect because performance testing is not a form of functional testing. Performance testing is used to assess the software's performance under various conditions, such as load, stress, and scalability.
Option D) Security testing - This option is incorrect because security testing is not a form of functional testing. Security testing is conducted to identify vulnerabilities and weaknesses in the software's security measures.
The correct answer is Option A) Boundary value analysis. This option is correct because it is a form of functional testing that focuses on testing the software at the boundaries of its input domain.