Which of the following is not regression test case ?

A. A representative sample of tests that will exercise all software functions
B. Additional tests that focus on software functions that are likely to be affected by the change
C. Tests that focus on the software components that have been changed
D. Low-level components are combined into clusters that perform a specific software sub-function

Explanation: Regression testing may be conducted manually, by re-executing a subset of all test cases or using automated capture or playback tools