The acid formed when propyl magnesium bromide is treated with carbon dioxide is:

Identify the product $C$ in the following reaction sequence:
$1$-bromo-$4$-chlorobenzene $+ Mg (1 \text{ mole})$ $\xrightarrow{THF} A$ $\xrightarrow{CO_2} B$ $\xrightarrow{H^+} C$

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:

If ethylene,carbon monoxide and water are heated at high temperature,which of the following is formed?

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

What is the product of the following reaction?
$Hex-3-ynal$ $\xrightarrow[(ii) PBr_3]{(i) NaBH_4}$ $\xrightarrow[(ii) CO_2 / H_3O^{+}]{(i) Mg / ether}$ ?