Which one of the following gives a yellow precipitate with iodine and $NaOH$ solution?

The above reduction can be best carried out by

The major product $(Y)$ in the following reactions is
$CH_3-CH(CH_3)-C\equiv CH$ $\xrightarrow[H_2O]{HgSO_4, H_2SO_4} X$ $\xrightarrow[(ii) \ conc. H_2SO_4 / \Delta]{(i) \ C_2H_5MgBr, H_2O} Y$

Which of the following aldehydes is most reactive towards nucleophilic addition reactions?

The product $(B)$ in the above reaction is:

Which of the following reagents can form a hydrazone with alkanone?