.如图所示，特性曲线a与b所表征的元件分别为（   ）。            

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69505' and id < 4502685 and id<>'4502685' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='69505' and id > 4502685 and id<>'4502685' order by id asc limit 5