— Jack, do you know anything about Doctor Brown?

— I ______ to him for years. I don't see how anyone else could do better. [ ]

A. went

B. will go

C. had gone

D. have been going

电流表指针偏转于右边T=100％处，无法回“O”位（）。

A.取出仪器光电管暗盒内硅胶，更换干燥处理过的硅胶

B.换灯

C.用电吹风从硅胶筒送人适量的干燥热风

D.换电源