Distractors are diagnoses

Distractors are diagnoses. A good wrong option is not random; it is what a specific misunderstanding produces:

• Off-by-one — < vs <=, index 0 vs index 1, length vs length - 1. The answer that is one position early/late.
• Shadowing blindness — price = price; in a constructor looks like initialization but assigns a field to itself. The wrong option shows the intended value; the truth is the default.
• Alias confusion — treating a copied reference as an independent object (or vice versa). Produces "mutated the copy" or "mutated the original" answers.
• Immutability blindness — assuming s = s + "!" inside a method changes the caller's string. Produces the concatenated option.
• Dispatch confusion — reading the reference type instead of the object type for overridden methods.
• Short-circuit blindness — assuming && evaluates both sides, producing an exception option that never happens.

When you miss a question, name which of these bit you. A miss with a name becomes a scanner during future traces; a miss without one repeats.