形式运算阶段的标志是守恒概念的形成。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='27574' and id < 2273221 and id<>'2273221' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='27574' and id > 2273221 and id<>'2273221' order by id asc limit 5