儿童认知发展到达具体运算阶段的标志是（ ）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='30754' and id < 2476144 and id<>'2476144' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='30754' and id > 2476144 and id<>'2476144' order by id asc limit 5