Compounds A and C in the following reaction are:

\(\mathrm{\small{{CH}_3 {CHO} \xrightarrow[{(ii) ~H_{2}O}]{(i) ~CH_{3}MgBr}({A}) \stackrel{{H}_2 {SO}_4}{\longrightarrow}({B}) \xrightarrow[]{Hydroboration \ oxidation}(C)}}\)

1.  Identical                               

2.  Positional isomers

3.  Functional isomers       

4.  Optical isomers



Hint: A and C both are alcohols

The reactions are as follows: 

CH3CHO(ii)H2O(i)CH3MgBrCHC|
CH3HOHDehydrationH2SO4,CH3C|
H=CH2
(HydroborationOxidation)(i)BH3(ii)H2O2/OHCH3CH2CH2OH

So structure A and C are the positional isomers because parent chain is same in both the compound but position of -OH group is different.

CH3C|HOHandCH3CH2-CH2-OH
CH3  


Hence, option (2) is correct.