The correct option is B dentine
Teeth, like bones, are living structures. They rest in a specially designed cavity in the bones of the jaw and have a supply of blood and nutrients to them through their base. The crown is the outside of the part of the tooth that is above the jaw bone, it is the part that does all the hard work. It is capped with an extra hard substance called enamel. The rest of the tooth is relatively softer but still harder than bone. Beneath the enamel, making up the bulk of the tooth is dentine and within the centre is the pulp cavity.