The correct response would depend on the specific characteristics of the image in question. Based on the options provided, if the image shows perspective with depth where lines converge to two distinct points, then "two vanishing points" would be the appropriate choice. If the image emphasizes depth in other ways, such as using size or color, another option may be more fitting.
However, without seeing the image, it is impossible to definitively answer which step the artist used. If you describe the image or its characteristics, I could help you select the correct option!