. . . . .
<form name=dati action=risp2.php method=POST>
. . . . .
<input type=submit value="A è in [B,C], in [D,E], o esterno ?">
. . . . .

. . . . .
<form name=dati action=risp3.php method=POST>
. . . . .
<input type=submit value="Ordina in modo crescente">
. . . . .

. . . . .
<form name=dati action=risp4.php method=POST>
. . . . .
<input type=submit value="Verifica">
. . . . .