They are trying to develop a convincing theory to explain how the needles work in preventing pain, or why a needle in the wrist, for example, would prevent the pain in the area of the mouth. (Passage 3)

【参考答案】

他们正在努力提出一种有说服力的理论，来解释针灸是怎样止痛的，或者举例来说，针扎在腕部为什么能治疗口腔疼痛。