Final answer:
The issue found during system testing is known as 'the defect', which is a result of 'the error' made by the programmer.
Step-by-step explanation:
When a tester finds that an input field accepts values beyond the intended upper boundary, this issue is known as D. the defect. The mistake made by the programmer due to a distraction is termed C. the error. It is the human action that led to incorrect results. The error in programming logic is the cause of the defect found during system testing. This defect is what causes the system to accept those invalid input values, which could potentially lead to failures when the software is in operation. A failure occurs if and when the defect manifests as incorrect behavior or results during execution.