A.16 B.11 C.14 D.15
A.BCDEF B.BCDEFG C.BCPQRST D.BCDEFEF
A.串中不同字符的個數(shù) B.串中不同字母的個數(shù) C.串中所含字符的個數(shù) D.串中不同數(shù)字的個數(shù)