Question: why one question lies four answers

with(Physics):with(combinat):
comn := choose([u, v, mu, nu], 2):

def := seq(seq(seq(Physics[`.`](Dagger(Ket(aa, k)), Ket(bb, m)) = Physics[`.`](Ket(bb, m), Dagger(Ket(aa, k))), `in`(aa, comn[i][1])), `in`(bb, comn[i][2])), i = 1 .. nops(comn)), seq(seq(seq(Dagger(Physics[`.`](Dagger(Ket(aa, k)), Ket(bb, m)) = Physics[`.`](Ket(bb, m), Dagger(Ket(aa, k)))), `in`(aa, comn[i][1])), `in`(bb, comn[i][2])), i = 1 .. nops(comn));
Setup(def):

d1 := Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Bra(nu, p), Bra(mu, q)), Bra(u, m)), Bra(v, q)), Ket(nu, m)), Ket(mu, n)), Ket(u, p)), Ket(v, q));
    delta[p, m] delta[q, n] Physics:-*(Physics:-Ket(u, p),Physics:-Ket(v, q))

d2 := Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Bra(v, p), Bra(u, q)), Bra(mu, m)), Bra(nu, q)), Ket(nu, m)), Ket(mu, n)), Ket(u, p)), Ket(v, q));
                                                 2
              delta[m, q] delta[m, n] delta[p, q]

d3 := Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Bra(nu, p), Bra(mu, q)), Bra(u, m)), Bra(v, q)), Ket(nu, m)), Ket(u, p)), Ket(v, q)), Ket(mu, n));
delta[p, m] Physics:-*(Physics:-Ket(u, p), Physics:-Ket(v, q),Physics:-Ket(mu, n))

d4:= Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Physics[`.`](Bra(nu, p), Bra(mu, q)), Bra(u, m)), Bra(v, q)), Ket(u, p)), Ket(v, q)), Ket(mu, n)), Ket(nu, m));
                               2           
                    delta[p, m]  delta[q, n]