儿童个体发展表现出的几个普遍特点是( )
A.顺序性
B.不平衡性
C.阶段性
D.协调性
E.差异性
参考答案:A,B,C,D,E
Great changes __________ in this city over the past five years.
A.took place
B.have been taken place
C.were taken place
D.have taken place
简述炭黑粒子的生成理论步骤。