题干
— I wonder how the girl got lost.
—She may have been separated from the other students and ______ have heard anyone when the thunder started.
A：mustn't
B：needn't
C：couldn't
D：shouldn't
答案(点此获取答案解析）
C
2SO3，平衡时SO3为n mol，在相同温度下，分别按下列配比在上述容器中放入起始物质，平衡时SO3的物质的量可能大于n的是（ ）