个体不同系统在发展的速度、起迄时间、到达成熟的时间有不同的进程指的是( )
A.发展的阶段性
B.定向性
C.不平衡性
D.差异性
参考答案:C
This kind of cloth _______ well. I think it is worth _______.[ ]
A. washes; buying
B. is washed; buying
C. washes; to be bought
D. is washed; to be bought
氧气瓶通常由瓶体、瓶箍和()等部分组成。