Our Chinese teacher told us         interesting story and         story was about Thomas Edison.

A．an; a

B．the; the

C．a; the

D．an; the

SSJ800/2×40型伸缩带式输送机减速器的是采用（）圆锥圆柱齿轮传动。

A、三级

B、四级

C、二级

D、一级