At One Time, Chondrichthyes Were Thought to Have Split Off

At one time, Chondrichthyes were thought to have split off from other vertebrates before the evolution of bone. Now we have concluded that the Chondrichthyes split off after the evolution of bone had started. This change demonstrates ________.

A) characteristics can be lost in evolution
B) evolution is one-way and straight line
C) hagfishes and lampreys have ancestors with bone
D) cartilage contributes to keeping sharks light so they do not sink