The text boxes in the left panel have been placed in a random order. Restore the original order by dragging the text boxes from the left panel to the right panel.
a) Black keys were traditionally made of ebony, and the white keys were covered with strips of ivory. However, since ivory-yielding species are now endangered and protected by treaty, makers use plastics almost exclusively.
c) Also, ivory tends to chip more easily than plastic.
b) Today they are usually made of spruce or basswood. Spruce is typically used in high-quality pianos.
d) In the early years of piano construction, keys were commonly made from sugar pine.