—________did your uncle leave his hometown?

—He ________ for nearly twenty years.

A．When; has left

B．When; has been away

C．How long; has left

D．How long; has been away

下列属于监理单位不履行合同义务的有（）

A.无正当理由单方解除合同

B.无正当理由不履行合同约定的义务

C.未完成合同约定范围内的工作

D.发出错误指令，导致工程受到损失等