Natural uncoupler is ?

Ans. is 'a' i.e., Thermogenin Amongst the given options, a, b and c are uncouplers.However, only thermogenin, among these three is a natural (physiological) uncoupler.UncouplesAs the name suggests, these componds block the coupeling of oxidation with phosphorylation. These compounds allow the transfer of reducing equivalents in respiratory chain but prevent the phosphorylation of ADP to ATPdeg by uncoupling the linkage between ETC and phosphorylation. Thus the energy instead of being trapped by phosphorylation is dissipated as heat. Uncouplers may be :-Natural :- Thermogenin, thyroxineSynthetic :- 2, 4-dinitrophenol (2, 4-DNP), 2, 4-dinitrocresol (2, 4-DNC), and CCCP (chlorocarbonylcyanidephenyl hydrazone).