Walking Along a Beach, You Find a Section of an Adult

Walking along a beach, you find a section of an adult grey whale's vertebral column with three vertebra. Sandwiched between two of the whale vertebrae is a disc of material. You poke it and the vertebrae with your finger. What do you expect, and why?

A) The bone will be harder than the intervertebral disc, because the bone is mineralized and the disc is a wall of connective tissue surrounding a core of "jelly."
B) The bone and the intervertebral disc will be the same hardness, because they are both skeletal composite materials.
C) The bone and the intervertebral disc will be the same hardness, because their having the same physical properties allows the skeleton to work as a functional unit.
D) The bone will be softer than the intervertebral disc, because it is the type of bone formed first as cartilage and retains its cartilaginous "framework" even in adult animals.