1. (2020高二上·丽水期末) 有如下VB程序段：

Dim x As String, s As String

x = Text1.Text: s=""

For i = 1 To Len(x)

    c = Mid(x, i, 1)

    If c = "a" Then

        s = s + "z"

    Else

        s = s + Chr(Asc(c) - 1)

    End If

Next i

在文本框Text1中输入“dream”，执行该程序段后，变量s的值是（    ）