单项选择题

A、应靠近主节点,偏离主节点的距离不应大于600mm
B、应靠近主节点,偏离主节点的距离不应大于300mm
C、应远离主节点,偏离主节点的距离不应小于400mm
D、应远离主节点,偏离主节点的距离不应小于600mm