I'd have to go with A. The rhino picture. The image is composed of what looks like notches or "gouges" used by a sharp tool, which removes certain areas by gouging them out with the tool and then leaving the actual print on the top of the surface. Often, a sort of paint roller would be passed over the surface image. The gouged out portions would not be pressed by the roller. Very cool and were used in many printing presses when they used templates.
Simple Explanation Reason - Why it was difficult is because of learning the technique. Since it was less common then Printmaking used with etching. Credit Researched - Engraving - Wiki-Pedia
