题干
They_____ old then. They_______old now. （ ）
A：weren't, are
B：weren't, was
C：wasn't , are
答案(点此获取答案解析）
A
They_____ old then. They_______old now. （ ）
A：weren't, are
B：weren't, was
C：wasn't , are
4NO（g）＋6H2O（g）在10L密闭容器中进行，半分钟后，水蒸气的物质的量增加了0.45mol，则此反应的速率可表示为（ ）
