请选择ABCD1[8z;V(k1} My parents live in a small village.They always keep candles in the house _________ there is a power cut.(K+x1Y1m3b8R9t5y+c9u2W
A.if(K+x1Y1m3b8R9t5y+c9u2W
B.unless(K+x1Y1m3b8R9t5y+c9u2W
C.in case(K+x1Y1m3b8R9t5y+c9u2W
D.so that(K+x1Y1m3b8R9t5y+c9u2W