premise: Two women sit at desks in a large room with white walls. hypothesis: The women are sitting in a room with black walls.
contradiction: Sentence 1 states that there are two women. There is no indication of the number of women in the room - instead it just says "the women." "The women" could mean that there are more than two women in the room but not less than two women.  Sentence 1 states that the women are sitting in desks. In sentence 2 the women could be sitting on the floor of the room.   In sentence 1 the room is described as large. In sentence 2 there is no description of the size of the room.   Sentence 1 the walls are white. Sentence 2 the walls are black. The walls are difference colors.