---I called you last night, but nobody answered.
---Oh, I usually off my cellphone by 9:00 p.m.
A. switched
B. have switched
C. switch
D. had switched
网友回答
A. switched
B. have switched
(答案→)C. switch
D. had switched
解析：句意：--我昨天晚上给你打电话了，但是没人接。--哦，我通常在晚上9点以后关机。因为这里指的是过去通常做某事，所以应该用一般过去时，故选C。