What is the characteristic odor of nitrobenzene?

What is the product formed when a $Grignard$ reagent $(RMgX)$ reacts with acetone $(CH_3COCH_3)$?

Upon treatment with $I_{2}$ and aqueous $NaOH$, which of the following compounds will form iodoform?

Identify the organic compounds $P$, $Q$, and $R$ in the following reaction sequence: $C_3H_6 \xrightarrow[ii) H_2O_2/NaOH]{i) BH_3} P \xrightarrow[anhydrous medium]{CrO_3} Q \xrightarrow[ii) H_3O^+]{i) CH_3MgBr} R + Mg(OH)Br$.

The given reaction is: $C_6H_5-CHO + C_6H_5-CHO \xrightarrow{Na_2[Fe(CO)_4]} C_6H_5-COOCH_2-C_6H_5$

Arrange these compounds in decreasing order of reactivity for the nucleophilic addition reaction :
$I.$ Acid chloride $II.$ Aldehyde
$III.$ Ketone $IV.$ Ester
Select the correct answer from the codes given below :