发电机单位时间内输入能量和输出能量的比值称为（）。（0.5）

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69421' and id < 4494878 and id<>'4494878' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69421' and id > 4494878 and id<>'4494878' order by id asc limit 5