帮忙一道VB题

Option Explicit

Private Sub Form_Click()
Dim a(20) As Integer
Dim i As Integer
Dim b As Integer, c As Integer, e As Integer, f As Integer, g As Integer
Dim S
For i = 1 To 20
a(i) = Int(Rnd * 100 + 1)
S = S & Str(a(i)) & Space(3)
If i Mod 4 = 0 Then
Print S
S = ""
Print
End If
If a(i) >= 90 Then
b = b + 1
End If
If a(i) >= 80 And a(i) < 90 Then
c = c + 1
End If
If a(i) >= 70 And a(i) < 80 Then
e = e + 1
End If
If a(i) >= 60 And a(i) < 70 Then
f = f + 1
End If
If a(i) < 60 Then
g = g + 1
End If
Next i

Print "90分以上的学生有" & b & "个, 80 - 90 分的学生有; " & c & "个"
Print "70-80分的学生有" & e & &qu