Assertion:\[N{H_4}HC{O_3}\]exists in solid state.
Reason:Alkali metals form solid bicarbonates.
(A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
(B) Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
(C) Assertion is correct but Reason is incorrect.
(D) Assertions are incorrect and Reason are correct.

Hint: As we know that Ammonium bicarbonate is a colourless substance that easily gives off carbon dioxide, water and ammonia and we also know that group alkali metals are highly basic in nature. Alkali metals react with various oxides, hydroxides, halides etc to form different stable compounds.

Complete answer:As we know that Alkali metals are highly basic in nature and they are highly electropositive as well so they form solid and stable carbonates and bicarbonates like sodium carbonate and sodium bicarbonate. Lithium is an exception in this group of metals due to its low electropositive nature but it forms a compound with bicarbonate in aqueous solution only. Similarly the bicarbonates of alkali earth metals do not exist in solid state instead they also exist in solutions only.
We also know that all alkali metals dissolve in liquid ammonia and give deep blue colour solutions which contain ammoniated cation and electrons.
Ammonium bicarbonate also exists as a solid and naturally occurring in nature and appears white crystalline in solid form with an odour of ammonia. It is produced when carbon dioxide reacts with ammonia and water which we can show through this equation:
$C{O_2} + N{H_3} + {H_2}O \to (N{H_4})HC{O_3}$
Therefore we can say that both assertion and reason are correct but reason is not the answer to the assertion.

Hence the correct answer is (B).

Note: Ammonium bicarbonate formed is thermally unstable that is why the solution of formation of ammonium bicarbonate is generally kept cold that allows its precipitation as a white crystallised solid. Metal hydrogen carbonates are basic and produce salts, water and carbon dioxide whenever they react with an acid.