Answer:
d. tortillians
Explanation:
Artists very often use chamois leather widely known as 'shammy' in charcoal and pencil drawing, as blending tool which can soften pencil tones. Shammy is a smaller piece of lamb skin treated by oils.
The gum is not only a means of wiping out a mistake from a drawing, but also a way to draw white lines from surfaces that are already saturated with graphite or carbon, in other words - to work in the negative and blend pencil or charcoal tone.
Because it is a soft and sticky rubber, it will be easy for you to mold exactly the rubber you need to remove coal dust or graphite from paper. It won't stain on the drawing, nor is it too strong to tear the paper due to frequent corrections, so it's great for beginners and students.
