节理系
参考答案：
在一次构造作用的统一应力场中形成的产状呈规律性变化的一群节理叫节理系。
Nine in ten high school students say there are significant differences in their attitude toward chatting on line, compared with _________ of their parents.
A．those
B．that
C．it
D．one
投标保证金的数额最高不得超过( )万元。
A．50B．60C．80D．100
