— You never feel worried before an exam, how can you?

— Well, I've been working hard all the time. Surely I am _____ any exam. [ ]

A. busy with

B. afraid of

C. ready for

D. interested in

分别来自两个不同变电站，或来自不同电源进线的同一变电站内两端母线，为供电（）电源。