Deficiency of which of the following leads to dermatitis,diarrhea,and dementia?

The conversion of fatty acids into $CO_2$ and $H_2O$ is called $........$ process,and the synthesis of fatty acids from acetyl $CoA$ is called $........$ process.

Which of the following represents the correct structure of cytosine?

Assertion $A$: Water is an efficient solvent.
Reason $R$: Polar nature is an important property of water.
Which option is correct for Assertion $A$ and Reason $R$?

Match the following:

$(a)$ Inhibitor of catabolic reaction	$(i)$ Ricin
$(b)$ Contains peptide bond	$(ii)$ Malonate
$(c)$ Cell wall material in fungi	$(iii)$ Chitin
$(d)$ Secondary metabolite	$(iv)$ Collagen

Select the correct option:

How many covalent bonds are present in the water molecules shown in the given figure?