Each structure shown is treated with methylmagnesium bromide followed by aqueous work-up. Select the structure(s) that give an achiral alcohol.

Pentan-3-one gives 3-methylpentan-3-ol, in which two ethyl groups are identical so the carbinol carbon is not a stereocentre. Propanone gives 2-methylpropan-2-ol, which is also achiral. Benzaldehyde gives 1-phenylethanol and ethyl isopropyl ketone gives 3,4-dimethylpentan-3-ol, in which the carbinol carbon carries four different groups, so both are chiral.