Select the figure that completes the logical sequence. The sequence shows an equilateral triangle at each step, changing its orientation and the color of its top vertex. In step 1, the triangle points up and the top vertex is black. In step 2, the triangle has rotated 120 degrees clockwise (pointing down) and the top vertex is white. In step 3, the triangle has rotated again 120 degrees clockwise (pointing up and to the right) and the top vertex is black. Which figure corresponds to step 4?