房性期前收缩的心电图表现是（)

A、反映系统内部要素与外在行为间的因果关系 The index system should reflect the causal relationship between the internal elements of the system and the external behavior
B、反映特定时间尺度内事物的变化趋势 The index system should reflect the changing trend of things within a given time scale
C、应反映尽少的信息 The index system should reflect as little information as possible
D、应简明易懂，利于公共政策制定和文化变革 The index system should be easy to understand and facilitate public policy formulation and cultural change

A、阳极就是正极，阴极就是负极
B、阳极就是负极，阴极就是正极
C、正极发生还原反应，负极发生氧化反应
D、三种说法都不对

A、一
B、二
C、三
D、无法确定