Synthesis of vitamin $A$ in the body takes place in

Fill in the blanks appropriately:
Organ: Excretory wastes
$(a)$ Kidneys: .......
$(b)$ Lungs: ...........
$(c)$ Liver: ...........
$(d)$ Skin: ...........

What is the primary function of the hormone Erythropoietin?

Components present in sweat $- P$
Components present in sebum $- Q$
$I -$ Sterols,$II -$ Waxes,$III - NaCl$,$IV -$ Hydrocarbons,
$V -$ Lactic acid,$VI -$ Small amounts of urea
Select the correct option for $P$ and $Q$.
$P \quad Q$

Kidneys are not the only organs of excretion; their work is supplemented by

In which of the following is harmful uric acid converted into potassium sulfocyanide?