Function wordsOK(string1 As String, string2 As String) As boolean
    If Mid(string1, Len(string1), 1) = Mid(string2, 1, 1) Then
        Return True
    End If
    Return False
End Function

Function Amb(A() As String, B() As String, C() As String, D() As String) As String
    Dim As Integer a2, b2, c2, d2
    For a2 = 0 To Ubound(A)
        For b2 = 0 To Ubound(B)
            For c2 = 0 To Ubound(C)
                For d2 = 0 To Ubound(D)
                    If wordsOK(A(a2),B(b2)) And wordsOK(B(b2),C(c2)) And wordsOK(C(c2),D(d2)) Then
                        Return A(a2) + " " + B(b2) + " " + C(c2) + " " + D(d2)
                    End If
                Next d2
            Next c2
        Next b2
    Next a2
    Return "" 'Cadena vacía, por ejemplo, falla
End Function

Dim As String set1(2), set2(2), set3(2), set4(1)
set1(0) = "the"    : set1(1) = "that"     : set1(2) = "a"
set2(0) = "frog"   : set2(1) = "elephant" : set2(2) = "thing"
set3(0) = "walked" : set3(1) = "treaded"  : set3(2) = "grows"
set4(0) = "slowly" : set4(1) = "quickly"

Dim As String text = Amb(set1(), set2(), set3(), set4())

If text <> "" Then
    Print !"Correct sentence would be:\n" + text
Else
    Print "Failed to fine a correct sentence."
End If
Sleep