Which of the following react with $NaHSO_3$?

The solution of Fehling $B$ contains . . . . . . .

When acetaldehyde is heated with Tollen's reagent,what is obtained?

Which of the following compounds will give a positive iodoform test?

Compound $P$ $(C_{8}H_{8}O)$ gives a red-orange precipitate with $2,4-DNP$ reagent and it does not reduce Fehling's reagent. On drastic oxidation with chromic acid, $P$ gives an aromatic product $Q$ that produces effervescence on treating with aqueous $NaHCO_{3}$. Compound $P$ and $Q$, respectively, are:

An organic compound $(A)$ with molecular formula $C_8H_8O$ forms an orange-red precipitate with $2,4-DNP$ reagent and gives a yellow precipitate on heating with iodine in the presence of sodium hydroxide. It neither reduces Tollens' or Fehlings' reagent,nor does it decolourise bromine water or Baeyer's reagent. On drastic oxidation with chromic acid,it gives a carboxylic acid $(B)$ having molecular formula $C_7H_6O_2$. Identify the compounds $(A)$ and $(B)$ and explain the reactions involved.