The is the top part of the tooth that is covered by .

Enamel

Explanation:

The enamel is the outer layer of the crown. It is the hardest substance that can be found in the human body. The other parts include a middle layer that is called dentin and the inner layer is called the dentin. It is composed of minerals up to 96% and the rest part constitutes the water, organic material, and others. The primary mineral content is the hydroxyapatite.

Tooth enable is necessary for the protection of teeth against the action of bacteria and acid in the mouth.

answer; i do believe that the correct answer is (b)

i think it's the first one because doctors aren't the ones who get rid of the old needles. most of them time it's not even doctors who give you shots, it's nurses.