Barbituric acid and its derivatives are well known as

Given Data: It is asked in the question what are Barbituric acid and its derivatives are well known as

Concept Used: Tranquilisers 

Detailed Solution: 

The drugs which act on the central nervous system (CNS) and help in reducing stress and fatigue by inducing a sense of well-being are called tranquilizers. They are psychotherapeutic drugs. The most commonly used tranquilizers are barbituric acid and its 5, 5-disubstituted derivatives such as veronal, luminal and seconal.

Hence, the required option is A).