We are being asked to explain the following apparently paradoxical situation: that even when the technology is functioning correctly, it is not a perfect safeguard.
Answer choice C is about what happens if plane's automatic flight technology malfunctions. If the flight technology malfunctions, then it is not working perfectly so it is not related to the phenomena we are trying to describe.
Answer choice E allows to resolve the paradox because even if the technology is working perfectly, it is designed to execute humans' commands so answer choice E allows us to introduce human error as an explanation.