1. (2019高二下·衢州期末) 有 VB 程序段如下：

s = "2019appreciate": sum = 0

For i = 1 To Len(s)

ch = Mid(s, i, 1)

If ch >= "a" And ch <= "z"

Then m = Asc(ch) - Asc("a") + 1 a(m) = a(m) + 1

End If Next i

For i = 1 To 10

If a(i) > 0

Then sum = sum + 1

Next i

数组 a 各元素的初始值都为 0，执行该程序段后，则变量 sum 的值为（   ）