[多项选择]中国4,000年前就已经出现了用于针灸(acupuncture)的针，最初的针是石做的，后来发展到铜针、金针或者银针，今天用于针灸的针一般都是钢做的。针灸的发展是响应了一个理论——人体里有很多特殊的穴位(meridian point)把内部器官联通起来并且血气在经脉里流动。根据这个理论，血气的流动被打断的时候就产生了疾病，于是把针捅进皮肤底下并且旋转就可以打通经脉，恢复血气的正常流通。

参考答案:Acupuncture needles dating from D,000 years ago have been found in China. The first needles were stone, later, bronze, gold, or silver was used, and today’s needles are usually made of steel. Acupuncture was developed in response to the popular theory that there are special meridian points on the body connecting to the internal organs and that vital energy flows along the meridian lines. According to this theory, diseases are caused by interrupted energy flow, and inserting and twirling needles restores normal flow.