Reaction of Chlorobenzene with Mg in dry ether
Chlorobenzene (C6H5Cl) undergoes a reaction with magnesium (Mg) in dry ether (C2H5OC2H5) to give a compound (A). This reaction is known as the Grignard reaction.

Formation of Compound (A)
- The reaction between chlorobenzene and magnesium occurs due to the presence of an electron-deficient carbon atom (the carbon atom in chlorobenzene bonded to the chlorine atom).
- The magnesium atom donates a pair of electrons to the carbon atom, forming a bond between them.
- As a result, the chlorine atom detaches from the carbon atom and forms magnesium chloride (MgCl2), which is soluble in the ether solvent.
- The compound formed after the reaction is the addition product of magnesium and the carbon atom from chlorobenzene, which is compound (A).

Reaction of Compound (A) with Ethanol
- Compound (A) obtained from the reaction of chlorobenzene with magnesium reacts with ethanol (C2H5OH).
- In this reaction, the carbon atom in compound (A) forms a new bond with the oxygen atom in ethanol, resulting in the formation of a new compound.
- The hydrogen atom attached to the oxygen atom in ethanol is transferred to the carbon atom in compound (A).
- The final product formed after the reaction is benzene, which confirms that compound (A) is actually benzene.

Explanation of Correct Answer: Option 'B' (Benze)
The correct answer is option 'B' (Benzene) because the final product obtained after the reaction of compound (A) with ethanol is benzene. This is confirmed by the reaction mechanism and the formation of the new carbon-oxygen bond, resulting in the transformation of compound (A) into benzene. Hence, option 'B' is the correct answer.

Overall, the reaction between chlorobenzene and magnesium in dry ether followed by the subsequent reaction with ethanol leads to the formation of benzene, making option 'B' the correct choice.