下图电路中R为（）时，获得功率最大。 

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SQL Error: select id,body,options from ***_enewstiku where sourceid='32671' and id < 2598853 and id<>'2598853' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='32671' and id > 2598853 and id<>'2598853' order by id asc limit 5