Crypts of Lieberkühn are found in:

The wall of the colon exhibits small sac-like structures formed due to contractions, which are called .......

Kupffer cells of the liver help in . . . . . . .
$i$. Detoxification
$ii$. Synthesis of vitamin $A, D, K$ and $B_{12}$
$iii$. Emulsification of fats
$iv$. Deamination of amino acids
$v$. Phagocytosis

The mucus-secreting cells of the intestinal mucosal epithelium are $...............$ .

Which of the following vitamins is synthesized by bacteria in the animal body?

Explain the terms thecodont and diphyodont.