Electronegativity of carbon atoms depend upon their state of hybridization. In which  of the following compounds, the carbon marked with asterisk is most  electronegative?

[Step 1]:
Electronegativity of carbon atom depends on their state of hybridization. More S- character more the electronegativity.
[Step 2]:
$\underset{25\mathrm{\%}\mathrm{S}}{{\mathrm{SP}}^3}<\underset{33\mathrm{\%}\mathrm{S}}{{\mathrm{SP}}^2}<\underset{50\mathrm{\%}\mathrm{S}}{\mathrm{SP}}$

[Step 3]:
Thus SP-carbon has highest electronegativity. i.e, option 3 is correct.