---- What about _____ lecture?

---- It’s too tiring, as is known, _____ lecture for me.

A．a; the

B．the; the

C．the; /

D．the; a

用显微镜观察标本时，若所用的目镜是10X，物镜是15X，则被观察的物体放大了(      )

A．5倍

B．150倍

C．15倍

D．50倍