叠层石
参考答案：
主要由蓝藻和绿藻生物分泌的粘液粘结碳酸钙质而形成的具叠层构造的岩石，由亮层和暗层组成，亮层以碳酸钙质为主，暗层以蓝、绿藻为主。
— Can I buy Jane Ryre here?
— Sorry, but we'll call you as soon as it becomes _____. [ ]
A. present
B. available
C. convenient
D. inexpensive
简述脑电图检查分析内容。
