“作用的”的英语？

他对一些毒药的性质和作用的描述惊人地准确。Her description of the nature and action of poisons is amazingly accurate.腿筋是位于大腿后侧起支撑作用的肌肉。Hamstrings are supporting muscles at the back of the thigh.最后，他再也无能为力了，这也正是雅克发挥作用的时候。Finally, he could do n...