.图示电路中，电压源US=（    ）。

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69350' and id < 4489469 and id<>'4489469' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69350' and id > 4489469 and id<>'4489469' order by id asc limit 5