Which of the following testing techniques ensures that the software product runs correctly after the changes during maintenance?

Explanation

Regression testing is the re-execution of a subset of already-passed tests after a modification, to confirm that the change has not reintroduced faults or broken previously working behaviour. That is precisely the maintenance situation described. Path testing is a white-box technique for covering independent execution paths within a single unit, unit testing checks one module in isolation, and integration testing checks the interfaces between modules — none of them is defined by being run after a change. Regression testing is therefore the maintenance-phase safety net.