要经常注意检查主断路器转动轴（）是否松动，以免脱落后造成主断路器闭合不上。
参考答案：固定销子
We have ________ rules in our school. [ ]
A. too many
B. many too
C. too much
D. much too
什么是复合材料？其应具备哪些特征？
