如果变量a中保存字母"m"，则以下程序段执行后，变量Str$的值是 Select Case a$ Case "A" To "Z" Str$ = "Upper Case" Case "0" To "9" Str$ = "Number " Case "!", "?", ",", ") ", ";" Str$ = "Punctuaton" Case "" Str$ = "Null String" Case Is < 32 Str$ = "Special Character" Case Else Str$ = "Unknown Character" End Select