When I entered the step-classroom (阶梯教室), the lecture __________ and the audience __________ attentively.

A．began, listened

B．was begun, was listening

C．had begun, listened

D．had begun, were listening

计量检定过程包括了检查、加标记和（或）出具检定证书。检查一般包括计量器具（）的检查和计量器具的（）的检查等。

A.准确性，可靠性

B.准确性，稳定性

C.外观，计量特性

D.外观，准确性