sub wordsOK(string1$, string2$)
    return right$(string1$, 1) == left$(string2$, 1)
End sub

sub Amb$(A$(), B$(), C$(), D$())
    local a2, b2, c2, d2

    For a2 = 1 To arraysize(A$(), 1)
        For b2 = 1 To arraysize(B$(), 1)
            For c2 = 1 To arraysize(C$(), 1)
                For d2 = 1 To arraysize(D$(), 1)
                    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
            Next
        Next
    Next
    Return ""
End sub

Dim set1$(1), set2$(1), set3$(1), set4$(1)

void = token("the that a", set1$())
void = token("frog elephant thing", set2$())
void = token("walked treaded grows", set3$())
void = token("slowly quickly", set4$())

result$ = Amb$(set1$(), set2$(), set3$(), set4$())

If result$ <> "" Then
    Print "Correct sentence would be: ", result$
Else
    Print "Failed to fine a correct sentence."
End If