( )是显性课程的主要特征，是区分正式课程和非正式课程的主要标志。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='30345' and id < 2452740 and id<>'2452740' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='30345' and id > 2452740 and id<>'2452740' order by id asc limit 5