下图所示电路中的时间常数为（）。 

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SQL Error: select id,body,options from ***_enewstiku where sourceid='32631' and id < 2594718 and id<>'2594718' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='32631' and id > 2594718 and id<>'2594718' order by id asc limit 5