According to the extract, the words that describe Fredo's house imply that the house is full of metal, which means that the correct option is 1. Metal filled the house. This can be inferred because from the beginning of the text metaphorically the house becomes the lair, the hive, the storeroom and the complex of chambers of different iron animals. Also, the passage says: From wall to wall, from floor to ceiling the mountain of metal was broken only by a thin corridor. Based on that the readers can deduce that it was only a thing space without metal because there is a mountain of metal filling the house.