If an instruction clearly states the task but does not explain how success will be measured, what is the most important weakness?

Correct answer: Unclear evaluation criteria

An instruction is complete only when the performer knows what to do and what standard or result will show that the task has been completed successfully. If evaluation criteria are missing, people may produce different outcomes or be judged inconsistently. Option A identifies this weakness. Eye contact, courtesy, and sound level do not determine how written or spoken work will be evaluated.