Compound $(C)$ is

When liquid $A$ is treated with a freshly prepared ammoniacal silver nitrate solution,it gives a bright silver mirror. The liquid forms a white crystalline solid on treatment with sodium hydrogensulphite. Liquid $B$ also forms a white crystalline solid with sodium hydrogensulphite but it does not give a test with ammoniacal silver nitrate. Which of the two liquids is an aldehyde? Write the chemical equations of these reactions also.

Which of the following reactions does not represent the aldol condensation reaction?

$CH_3CHO$ $\xrightarrow{HCN} A$ $\xrightarrow{H_3O^+} B$. The product $B$ is

Which one of the following is the major product of the given reaction?

Which compound gives lactic acid on hydrolysis after reacting with $HCN$?