Chlorination of toluene in the presence of light and heat followed by treatment with aqueous NaOH and subsequently with dilute HCl gives benzoic acid. Let's break down the reaction steps to understand why this is the correct answer.

1. Chlorination of Toluene:
When toluene is subjected to chlorination in the presence of light and heat, substitution reactions occur, leading to the incorporation of chlorine atoms into the toluene molecule. This can result in the formation of a mixture of ortho, meta, and para isomers of chlorotoluene.

2. Treatment with Aqueous NaOH:
The next step involves treating the mixture of chlorotoluenes with aqueous NaOH. Aqueous NaOH is a strong base that can deprotonate the chlorotoluenes, resulting in the formation of sodium salts of the corresponding phenols. The deprotonation process occurs preferentially at the ortho and para positions due to the stability of the resulting phenoxide ions.

3. Acidification with Dilute HCl:
The final step is to acidify the mixture of sodium salts of phenols with dilute HCl. The addition of dilute HCl leads to the protonation of the phenoxide ions, resulting in the formation of the corresponding phenols.

Explanation:
By following these reaction steps, the chlorine atoms in chlorotoluene are replaced by hydroxyl groups, leading to the formation of cresols (methylphenols). However, the subsequent acidification step with dilute HCl converts the cresols into their corresponding carboxylic acids.

In this case, the product obtained after acidification is benzoic acid. This is because when the ortho and para isomers of cresols are protonated, they undergo rearrangement to form benzoic acid. On the other hand, the meta isomer of cresol does not undergo rearrangement and remains as 2,4-dihydroxytoluene.

Therefore, the correct answer is option D) benzoic acid, as it is the final product obtained after the chlorination of toluene, treatment with aqueous NaOH, and subsequent acidification with dilute HCl.