The correct choice is (a) Wall facing
For explanation: Stone blocks used in masonry can be dressed or rough, though in both examples: corners, door and window jambs, and similar areas are usually dressed. Stone masonry utilizing dressed stones is known as ashlar masonry, whereas masonry using irregularly shaped stones is known as rubble masonry. Both rubble and ashlar masonry can be laid in coursed rows of even height through the careful selection or cutting of stones, but a great deal of stone masonry is uncoursed.