教师在课堂上不断提供正例、反例，最主要的目的是(

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SQL Error: select id,body,options from ***_enewstiku where sourceid='32274' and id < 2568850 and id<>'2568850' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='32274' and id > 2568850 and id<>'2568850' order by id asc limit 5