任意时刻的三个对称分量的瞬时值之和和相量之和均为零。（    ）   

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68472' and id < 4420971 and id<>'4420971' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='68472' and id > 4420971 and id<>'4420971' order by id asc limit 5