W is the softest of the four substances tested. W is the hardest of the four substances tested. W can scratch Y. W can scratch X.
I gave my students this multiple choice question: Some students are performing hardness tests on several substances. X scratches Y. Y scratches Z. Z scratches W. Which of these statements best describes substance W's hardness?

Only one answer is correct among these 4 choices:
- W is the softest of the four substances tested.
- W is the hardest of the four substances tested.
- W can scratch Y.
- W can scratch X.

Could you tell me which one is correct?

W is the softest of the four substances tested.