Hello! Hubei college entrance examination mathematics auxiliary line can use pencil or gel pen, as long as the ruler is used to draw a dotted line to ensure cleanliness and neatness. Generally, the marking teacher doesn't care what pen you use. Of course, pencils are the best, and you can erase them with an eraser to prevent drawing mistakes. I hope the answer will satisfy you. Hehe, I didn't deduct points for the auxiliary line made with gel pen in the college entrance examination.