Power screws (motion/power transmission): target property for thread selection. For screws used to transmit power/motion (e.g., screw jacks, presses, lead screws), identify the desired efficiency characteristic. Choose the correct option.

Concept
Power-transmission screws (square/Acme threads) aim to minimize friction losses so that a larger fraction of input work becomes useful output. Thus a high efficiency is desirable. (Some applications may also require self-locking, but the general design goal for power transmission is higher efficiency than, say, fastening.)

Why not others

• Low efficiency wastes power and increases heating.
• Very fine threads are for precise adjustment, not necessarily for efficient power transmission.
• Strong teeth (wording fits gears; threads need strength, but efficiency is the key differentiator for this question).

Final Answer
High efficiency