The minimum number of carbon atoms in ketones which will show chain isomerism is:

Which of the following gives a positive iodoform test?

Among the following,the compounds which can be reduced with formaldehyde and conc. $aq.$ $KOH$ are $.....$

The reaction sequence is as follows:
Benzene + $CH_3Cl$ $\xrightarrow{Anhy. AlCl_3} A$ $\xrightarrow[(2) H_3O^+, \Delta]{(1) CrO_3 / (CH_3CO)_2O, 273-283K} B$
The incorrect statement about '$B$' is:

Consider the following reaction sequence:
$B \xleftarrow{NaBH_4} CH_2=CH-CHO \xrightarrow{H_2/Pt} A$
Identify $A$ and $B$.

Formaldehyde can be distinguished from acetaldehyde by the use of