Let's start by diagramming the stimulus. "One should not play a practical joke on someone if it shows contempt for that person or if one believes it might bring significant harm to that person."
"If" introduces a sufficient condition. Shows contempt for that person = SC Believes might bring significant harm to that person = MBSH Play a practical joke = PPJ
SC or MBSH ==> not PPJ contrapositive: PPJ ==> not SC and not MBSH
Ok, that's the principle.
Now the question stem asks us to identify the answer choice that is most justified by this principle.
Answer choice (C) is correct. There is no contempt (not SC) but it could bring significant harm (MBSH). MBSH is sufficient to conclude not PPJ.
Hope this helps. Please let us know if you have any additional questions.