串级试验变压器的串级数k4,则其效率为（）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='32665' and id < 2597937 and id<>'2597937' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='32665' and id > 2597937 and id<>'2597937' order by id asc limit 5