72. Which of the following description of laser cutting is incorrect？ (A)The laser will be unfocused, won't cut properly and the material might catch fire if the lens and mirrors are dirty. (B)Any vector file, such as Svg, Dxf, Pdf, etc. can be cut. (C)If there is a sustained flame, pause the job and call the staff. (D)During laser cutting, the focus can only be on the surface of the processing object.