<em>Corroboration </em>is the evidence that is backed up by the initial evidence. For example, a witness says that I saw a man in black coat entering the store and buying a bag. Later, the saleswoman, who is another witness testifies that she sold the bag to the man in a black coat. In this case, both witnesses confirm the situation and the evidences coincide. When there is no corroboration, there is not any available source to confirm the same information.
To those who do not know what to refer to:
Refer to "The Premature Burial", specifically this part: From the images of gloom which thus haunted me in dreams, I select for record but a single vision. I thought I was immersed in a cataleptic trance of more than usual duration and depth. Suddenly there came an icy hand upon my forehead, and an impatient, gibbering voice whispered the word "Arise!" within my ear.
I sat erect. The darkness was total. I could not see the figure of him who had woken me.
"Arise! did I not bid you arise?"
"And who," I demanded, "are you?"
D) shopping malls replaced downtown shopping areas
Hades does not believe that the other gods will help him search for the Helm of Darkness, so he doesn't tell any of the other guards that it is missing. Eventually, Percy helps him find the Helm of Darkness that was stolen by Luke, so Hades helps Percy out and returns his mother.
