Laughing gas is prepared by heating

Which of the following compounds is a tribasic acid?

Which of the following does not produce ammonia upon heating?

Atoms in a $P_4$ molecule of white phosphorus are arranged regularly in space in which of the following way?

Which is an incorrect match?

An inorganic salt $(A)$ is decomposed at about $523 \ K$ to give products $(B)$ and $(C).$ Compound $(C)$ is a liquid at room temperature and is neutral to litmus paper,while oxide $(B)$ on burning with white phosphorus,gives a dehydrating agent $(D).$ Compounds $(A)$,$(B)$,$(C)$ and $(D)$ will be identified as: