TableTAB1wascreatedusingthefollowingstatement:CREATETABLEtab1(c1INT,c2INT,c3INT,c4INT,c5INT);IfcolumnC1isuniqueandqueriestypicallyaccesscolumnsC1andC2together,whichstatement(s)willcreateindex(es)thatwillprovideoptimalqueryperformance?（）
A.CREATEUNIQUEINDEXxtab1ONtab1(c1)include(c2)
B.CREATEUNIQUEINDEXxtab1ONtab1(c1);CREATEINDEXxtab2ONtab1(c3)INCLUDE(c2)
C.CREATEUNIQUEINDEXxtab1ONtab1(c2,c1)
D.CREATEUNIQUEINDEXxtab1ONtab1(c2)INCLUDE(c1）
参考答案：A
