采用多层化学涂层技术的仪器（如VITROS250）报警噪音信号高，通常出现于（）

A.孵育器温度超出性能规格范围

B.硬件错误或由操作者导致的错误

C.样品量不足

D.高活性样品导致不规则的动力学反应过程

E.仪器检测到无效的干片电压或光度读数

_____ the waiter didn’t understand what the old lady was saying , he knew what she wanted.

A．Unless

B．Because of

C．Even though

D．Because