1. Identify each reaction product

We must check which reactions give carboxylic acid as the major product.

2. Reaction (A)

The substrate is a nitrile: $R-C\equiv N \xrightarrow[\text{mild condition}]{H^+/H_2O}$

Acidic hydrolysis of nitriles can proceed through the amide and finally to carboxylic acid, but under mild conditions the hydrolysis is not complete and the major product is generally the amide, not the acid.

So, (A) does not give carboxylic acid as major product.

3. Reaction (B)

$R-MgX \xrightarrow{CO_2} RCOO^-MgX^+ \xrightarrow{H_3O^+} RCOOH$

Grignard reagent with carbon dioxide followed by acidic workup gives a carboxylic acid.

So, (B) gives carboxylic acid.

4. Reaction (C)

$R-C\equiv N \xrightarrow{SnCl_2/HCl} \xrightarrow{H_3O^+}$

This is Stephen reaction. A nitrile is reduced to an iminium salt, which on hydrolysis gives an aldehyde: $R-C\equiv N \rightarrow R-CHO$

So, (C) does not give carboxylic acid.

5. Reaction (D)/(E in the printed list)

The substrate is a primary alcohol: $R-CH_2OH \xrightarrow{PCC}$

PCC oxidizes a primary alcohol only up to the aldehyde stage: $R-CH_2OH \xrightarrow{PCC} R-CHO$

It does not oxidize it to carboxylic acid.

So, this reaction does not give carboxylic acid.

6. Conclusion from the reactions

Only reaction (B) gives carboxylic acid as major product.

However, the options are written in a mismatched way using letters A, B, C, D while the reaction list itself contains labels A, B, C, D/E. From chemistry, the only definitely correct reaction is the Grignard + CO$_2$ reaction.

The stored answer says D: B and E only. This would mean the last reaction also gives acid, but PCC does not oxidize a primary alcohol to carboxylic acid. Hence the stored answer appears inconsistent with the reaction shown.

So the correct chemistry-based answer should be B only; since that option is not present, the given options likely contain a printing error.