Correct Answer - Option 3 : Currency
||Entomology is the study of insects.
||Hepatology is the study of the liver.
||Numismatics is the study of currency.
||Neonatology is a subspecialty of pediatrics that consists of the medical care of newborn infants.
Zoology → Zoology is the branch of biology that studies the animal kingdom.
Numismatics → Numismatics is the study or collection of currency, including coins, tokens, paper money, and related objects.
Hence, "Currency" is the correct answer.