Total number of stereoisomers of the compound, 2,4−dichloroheptane are:

Stereoisomers are isomers that have the same composition (that is, the same parts) but that differ in the orientation of those parts in space.

There are two kinds of stereoisomers: enantiomers and diastereomers.

${\mathrm{CH}}_3-\mathrm{C}\stackrel{*}{\mathrm{H}}\left(\mathrm{Cl}\right)-{\mathrm{CH}}_2-\mathrm{C}\stackrel{*}{\mathrm{H}}\left(\mathrm{Cl}\right)-{\mathrm{CH}}_2-{\mathrm{CH}}_2-{\mathrm{CH}}_3$

Here, total number of stereoisomers of the compound 4 but as one of the stereoisomers is meso compound, therefore the correct answer is 3.