The correct answer is option b i.e. cartilage.
Sharks do not have bones at all. They have cartilage instead of bones. Cartilage is white colored connective tissue. It is very flexible. Having cartilage instead of bones give many advantages to the sharks. Cartilage is much durable and light weighted than bones. Apart from this, cartilage is healed much faster than bones which are calcified and need long time for healing.
