This question examines the concept of motivation in task completion. The correct answer is 'B' because the fear of negative consequences can act as a strong motivator for task completion. Option 'A' is incorrect because while positive reinforcement is effective, the question specifies efficiency driven by a single factor, and fear of consequences is often more immediate. Option 'C' is incorrect because enjoyment of the task may not always be present. Option 'D' is incorrect because the desire to please others may not be a strong enough motivator for efficient task completion.