$Ph-C(=O)-CH_3$ $\xrightarrow[HCl]{NaNO_2} (A)$ $\xrightarrow[heat]{Ac_2O} (B)$ $\xrightarrow{H_3O^{+}} (C)$
Product $(C)$ of the above reaction is

Formic acid is obtained when

When $methyl \ cyanide$ is hydrolysed in the presence of an alkali,the final product is:

Consider the following reactions. From these reactions,which reaction will give carboxylic acid as a major product?
$(A)$ $R-C \equiv N \xrightarrow[(i) H^{+}/H_2O]{\text{mild condition}} R-CONH_2$
$(B)$ $R-MgX \xrightarrow[(ii) H_3O^{+}]{\text{(i) } CO_2} R-COOH$
$(C)$ $R-C \equiv N \xrightarrow[(ii) H_3O^{+}]{\text{(i) } SnCl_2/HCl} R-CHO$
$(D)$ $R-CH_2-OH \xrightarrow{PCC} R-CHO$
$(E)$ $\text{Benzoyl chloride} \xrightarrow[(ii) Br_2/H_2O]{\text{(i) } H_2/Pd-BaSO_4} \text{Benzoic acid}$
Choose the correct answer from the options given below:

Which of the following reagents is used for the conversion of $CH_3OH$ to $CH_3COOH$?

What will be the final product of the following reaction sequence?
$CH \equiv CH$ $\xrightarrow{CH_3MgBr}$ $\xrightarrow{CO_2/H_3O^+}$ $\xrightarrow{HgSO_4/H_2SO_4}$ $\xrightarrow{Ag_2O, \Delta} ?$