The correct answer is B.
In this passage from Ayn Rand's "Anthem", the narrator is exploring an abandonen tunnel made from an unknown material.
The narrator describes the walls as "hard and smooth" and "cold as glass". This depiction leads us to believe that the interior of the tunel is made of man-made concrete.
The narrator states that the material feel like stone but it is not, therefore answer A is incorrect. The walls are also said to be soft, making C incorrect as well. And there is no mention of the walls being wet, for what answer D is not correct either.
