（ ）没有端点，可以向两端（ ）。
直线；无限延伸
--I didn't know this was a one-way street, officer.
A．That's all right.
B．I don't believe you.
C．How dare you say that?
D．Sorry, but that's no excuse.
U常见化合价有＋4和＋6，硝酸铀酰[UO2(NO3)2]加热可发生如下分解。UO2(NO3)2UxOy＋NO2↑＋
O2↑，在600K时，将气体产物集于试管并倒扣水中，水充满试管。则生成的铀的氧化物化学式是[ ]
A．UO2
B．UO3
C．2UO2·UO3
D．UO2·2UO3
UxOy＋NO2↑＋