The answer is: They are subway or train tracks.
In the excerpt from "Anthem," by Ayn Rand, the narrator travels through an abandoned underground tunnel. She describes how they go below ground into a large tunnel and see the "long thin tracks of iron," which is not iron. They also touch the cold and smooth train or subway tracks, and crawl forward intending to find out where the tracks take to.
Remove! extraneous means irrelevent
C. It makes the skull sound like a toy ball, adding to the grandfathers casual view of the deaths caused by the battle.
A is not correct because if it was unavoidable, he would have said something different to describe the forgotten skull.
B. Is not correct because if it brought sad memories, he would not have brought it up, sad memories hurt.
D is not correct because he would have described much worse if he wanted to frighten the children
