Where do certain symbiotic microorganisms normally occur in the human body?

Teeth are chiefly made up of

Explain the structure of the mouth.

Human teeth are:
$(1)$ Of different types.
$(2)$ Embedded in a socket of the jaw bone.
$(3)$ Formed in two sets during their life.
This type of dentition is called:

Identify the parts $A$ and $B$ from the given cross-sectional diagram of the alimentary canal.

Which vitamin is synthesized in the colon by bacteria and absorbed by the colon itself?