题干
My parents live in a small village. They always keep candles in the house ___ there is a power out.
A：if
B：unle
C：so that
D：in case
答案(点此获取答案解析）
D
cC(g)＋dD(g)，反应达到平衡后，将气体体积压缩到原来的一半，当再次达到平衡时，D的浓度为原平衡的1.8倍，下列叙述正确的是
