A . A、寒武纪—奥陶纪—志留纪—泥盆纪—石炭纪—二叠纪
B . B、寒武纪—奥陶纪—泥盆纪—志留纪—石炭纪—二叠纪
C . C、寒武纪—奥陶纪—志留纪—泥盆纪—二叠纪—石炭纪
D . D、寒武纪—志留纪—奥陶纪—泥盆纪—石炭纪—二叠纪