An organic compound 'A' on reaction with NH₃ followed by heating gives compound B. Which on further strong heating gives compound C (C₈H₅NO₂). Compound C on sequential reaction with ethanolic KOH, alkyl chloride and hydrolysis with alkali gives a primary amine. The compound A is :

Melamine polymer is formed by the condensation of:

During the denaturation of proteins, which of these structures will remain intact?

Drugs used to bind to receptors, inhibiting is natural function and blocking a message are called: