OLT的中文名称是什么（）。
A.光接入模块
B.光接入单元
C.光分路器
D.光线路终端
参考答案：D
酸碱平衡(acid-basebalance)
Which condition is necessary for a substance to burn?（）
A.The temperature of the substance must be equal to or above its fire point
B.The air must contain oxygen in sufficient quantity
C.The mixture of vapors with air must be within the explosive range
D.All of the above
