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

Greater the s character of the hybrid orbitals, greater is the electronegativity. Thus, a carbon atom having sp hybrid orbital with 50% s character is more electronegative than those possessing sp² or sp³ hybridised orbitals.

The asterisk marked carbon in CH₃​−CH₂​−C≡CH is sp hybridized, hence, it is most electronegative.