Here's a problem to solve: 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?

Among the 4 following options, which is the correct answer?

- A: W is the softest of the four substances tested.
 
- B: W is the hardest of the four substances tested.
 
- C: W can scratch Y.
 
- D: W can scratch X.
 