The watch ______ unnoticed for several days before I found it.

A．had laid

B．had lain

C．had been laying

D．had been laid

施工升降机是一种使用工作笼（吊笼）沿（）作垂直（或倾斜）运动用来运送人员和物料的机械。

A.标准节

B.导轨架

C.导管

D.通道