英美学派对群落进行分类，主要是根据群落______原则的概念，所以有人也将该体系称为动态分类系统。
参考答案：动态发生演替
Before the final examination, many students have shown ______of tension. Some have trouble in sleeping while others have lost their appetite.
A．anxiety
B．marks
C．signs
D．remarks
醒脾升陷汤功效与作用
