结晶质
参考答案：
组成它们物质的质点（离子、原子、分子）有序的排列成空间格子状构造的固体物质
We should pay close attention to safety in schools because of frequent reports about accidents ____ students got injured or killed while in school.
A．which
B．for which
C．in which
D．what
电动自行车的“心脏”是电动机，它是利用 ______的原理工作的；关闭电源，人用力踩脚踏板，电动机就变成了“发电机”，从而实现“自发电”，它的发电原理是 ______．
