This excerpt probably should have included the verse following it, which
is "Here is Odysseus' hall, no hall like this!" So they are standing at
the gate at the home of Odysseus.
He has in fact made a long
journey home, so B could be correct. The journey did require patience
and endurance, so A could be correct. But I would go with D, happiness
upon returning home.
A reasonable argument could be made for
all of the above. Symbolism can be subjective, and each reader may
interpret things differently.
The gates Odysseus reaches are the ones to his home. He hears the harp as he stops his friend to revel in the sight of home. He even tells his friend "here is the beautiful place". While Odysseus did need patience and endurance for his long journey back home, at this point Odysseus is enjoyed the moment he has returned and nothing more. Also, he is priority is not reuniting with old colleagues. It is seeing his wife and son.
