Which of the following gives the iodoform test?

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

Among the following,the marked proton of which compound shows the lowest $pK_{a}$ value?

Assertion : Benzaldehyde is more reactive than ethanol towards nucleophilic attack.
Reason : The overall effect of $-I$ and $+R$ effect of phenyl group decreases the electron density on the carbon atom of $>C=O$ group in benzaldehyde.

Which of the following has the most acidic hydrogen?

$CH_3CH=CHCHO$ is oxidized to $CH_3CH=CHCOOH$ using