当未稳定原油中（）的含量低于0.5%（质量分数）时，一般不必进行稳定处理。
A.C1
B.C1~C2
C.C1~C4
D.C4~C6
参考答案：C
Francis, ____ born in Kentucky, lived and practised law in Missouri.
A．was
B．He was
C．who is
D．although
对下列二叉树
进行中序遍历的结果是______。
A．ACBDFEG
B．ACBDFGE
C．ABDCGEF
D．FCADBEG
进行中序遍历的结果是______。