Which of the following tests can be used to distinguish between $C_2H_5CHO$ and $(CH_3)_2CO$?

$3$-hydroxybutanal is formed when $(X)$ reacts with $(Y)$ in dilute $(Z)$ solution. What are $X, Y$ and $Z$?

Given below are two statements $:$
Statement $(I) :$ Vanillin,with the structure shown below,will react with $NaOH$ and also with Tollen's reagent.
Statement $(II) :$ Vanillin will undergo self-aldol condensation very easily.
In the light of the above statements,choose the most appropriate answer from the options given below $:$

Which of the following react with $NaHSO_3$?

Identify the reaction in which the carbonyl group of aldehydes and ketones is reduced to a methylene group upon treatment with zinc-amalgam and concentrated hydrochloric acid.

Consider the following reaction. The structure of the main product will be