先导通道的形成是以（   ）的出现为特征。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69351' and id < 4489482 and id<>'4489482' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69351' and id > 4489482 and id<>'4489482' order by id asc limit 5