Both figures shown in A and B are triangular pyramids. The base is a triangle, and the lateral sides are also triangles. Another example would be rectangular pyramids where the base is a rectangle, and the lateral sides are triangles.
Choice C is ruled out because cones aren't considered pyramids.
Choice D is a combination of a rectangular prism, and a rectangular pyramid stacked on top, so it's not purely a pyramid only. We can rule out choice D.
