4.(10.0分)用一千分尺( (Delta )_(UND)=pm 0.004mm) 测量-|||-某物体长度6次,其测量值为:4.298 mm、4.29-|||-6mm、4.288 mm、4.290mm、4.293mm、4.2-|||-95mm,已经求得标准误0.004mm,则计算不确-|||-定度UL的公式正确的是-|||-A. _(I)=sqrt ({{sigma )_(I)}^2}=0.004(mm)-|||-B. _(I)=sqrt ({{U)_(UND)}=0.004(mm);-|||-C. _(I)=sqrt ({{sigma )_(I)}^2+({Delta )_(U)}^2}=sqrt ({0.004)^2+(0.004)^4}=-|||-0.006(mm);-|||-D. _(I)=sqrt ({{sigma )_(t)}^2+({Delta )_(2)}^2}=sqrt ({0.004)^4+0.004}=.-|||-0.0053(mm)。