People living in the area where there is a lack of electricity often keep a supply of candles power failure.
A. in case of
B. once
C. even if
D. in course of
网友回答
(答案→)A. in case of
B. once
C. even if
D. in course of
解析：判断逻辑。此处为目的,in case of意思是“万一……”,in course of“在……过程中”,once是连词,用在此处句意不通。