交流电随时间而变化的特征性是（ ）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='25690' and id < 2159486 and id<>'2159486' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='25690' and id > 2159486 and id<>'2159486' order by id asc limit 5