An interdental crater has how many walls?

An interdental crater is a hole or gap between two adjacent teeth. In this context, a wall refers to the sides of the crater. A single crater would have two walls, one on either side. Therefore, the correct answer is two walls, or two sides, making option B the correct answer. Options A, C, and D are incorrect as they do not have the correct number of walls to fit the definition of an interdental crater. Option A only has one wall, option C has three walls, and option D has four walls, which does not match the criteria for an interdental crater.