The correct order of decreasing priority for functional groups in IUPAC nomenclature is:
Carboxylic acids (−COOH) > Sulphonic acids (−SO3H) > Esters (−COOR) > Acid halides (−COX) > Amides (−CONH2) > Nitriles (−CN) > Aldehydes (−CHO) > Ketones (>C=O) > Alcohols (−OH) > Thiols (−SH) > Amines (−NH2) > Alkynes (−C≡C−).
Checking the given options:
Option (A) is incorrect because −CHO has a higher priority than >C=O.
Option (B) is incorrect because −COOCH3 has a higher priority than −CONH2.
Option (C) correctly follows the priority order: −CONH2>−CHO>>C=O>−NH2>−C≡C−.
Option (D) is incorrect because −CN has a higher priority than −CHO.
Answer: −CONH2,−CHO,>C=O,−NH2,−C≡C−