knock knock at the door knock on a door
敲门;
knock knock at the door knock on a door
敲门;
knock knock at the door knock on a door
敲门;
cold-rolled steel strip cold-rolled strip cold-rolling strip steel cold-strip steel
冷轧带钢;
cold-rolled steel strip cold-rolled strip cold-rolling strip steel cold-strip steel
冷轧带钢;