句子:The amount of energy that can be produced anaerobically is a function of the amount of glycogen present—in all vertebrates about 0.5 percent of their muscles’ wet weight.
意思就是anaerobic energy reservesthe 正比于amount of glycogen ,而gly的量是muscle湿重的0.5%。想请教下 amount of glycogen present中的present怎么理解啊?作动词?形容词?觉得它好多余啊,直接amount of glycogen 就能表示gly的量了啊,这个present到底什么意思啊?~~~~请教请教~~~~~~