An organic compound 'A' with molecular formula CH₄O reacts with HI to give an alkyl iodide which than reacts with potassium cyanide to produce 'B'. Compound 'B' on reduction followed by reaction with HNO₂ gives an alcohol which on oxidation gives 'C'. Compound 'C' on oxidation followed by reaction with CH₃MgBr gives 'D' which on hydrolysis gives compound 'E' which is also an alcohol. 

Which is the strongest reducing agent among the following?

LiAlH₄

The correct answer is option 3. \(LiAlH_4\).

Among the options given, \(LiAlH_4\) (lithium aluminum hydride) is the strongest reducing agent.

\(LiAlH_4\) is a very powerful reducing agent because it can donate four hydride ions \((H^-)\). It is capable of reducing a wide variety of functional groups, including carbonyl compounds (aldehydes, ketones, carboxylic acids, esters), amides, and halides to their respective alcohols or lower oxidation states.\( LiAlH_4\) is typically used in non-aqueous solvents like ether due to its reactivity with water.
Comparison with Other Options:

\(H_2/Pd-C\) (hydrogen gas over palladium catalyst): This is a mild reducing agent commonly used for the reduction of alkenes or alkynes to alkanes, and for the hydrogenation of functional groups like ketones and aldehydes. It is not as strong as \(LiAlH_4\).

\(NaBH_4\) (sodium borohydride): \(NaBH_4\) is a selective reducing agent primarily used for reducing aldehydes and ketones to their respective alcohols. It is milder than \(LiAlH_4\) and cannot reduce carboxylic acids, esters, or amides.

Raney-Ni (Raney nickel): Raney nickel is a heterogeneous catalyst used in hydrogenation reactions. It is not a reducing agent in itself but facilitates hydrogenation reactions under specific conditions. Its reducing ability is moderate compared to \(LiAlH_4\).

Conclusion \(LiAlH_4\) stands out as the strongest reducing agent among the options listed due to its ability to donate hydride ions effectively across a wide range of organic functional groups. Therefore, the correct answer is \(LiAlH_4\). \(LiAlH__4\) is one of the strongest reducing agents in organic chemistry.