假设系统采用PV操作实现进程同步与互斥，若n个进程共享两台打印机，那么信号量S的取值范围为（）.

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SQL Error: select id,body,options from ***_enewstiku where sourceid='30131' and id < 2441885 and id<>'2441885' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='30131' and id > 2441885 and id<>'2441885' order by id asc limit 5