Which of the following on reaction with conc. $NaOH$ gives an alcohol?

The hydrogen atom bonded to the carbon designated by which number in $\stackrel{4}{C}H_3-\stackrel{3}{C}H_2-\stackrel{2}{C}H_2-\stackrel{1}{C}HO$ is most acidic?

In the reaction sequence,
$Cyclohex-2-en-1-one \xrightarrow[(ii) H_2O/H^+]{(i) CH_3MgBr/CuCl} (X)$
Product $(X)$ will be:

An organic compound neither reacts with neutral ferric chloride solution nor with Fehling solution. It,however,reacts with Grignard reagent and gives a positive iodoform test. The compound is:

Iodoform test is not given by

Which of the following compounds undergoes aldol condensation?