Which of the following makes ${\mathrm{PCl}}_5$ highly reactive?

Higher $\mathrm{P}—\mathrm{Cl}$bond length of axial sites than equitorial and high repulsion of equitorial shared pairs of electrons on axial shared pairs of electrons.

Division of sites to axial and equitorial positions.

Trigonal bipyramidal shape and geometry

Hybridisation ${\mathrm{sp}}^3\mathrm{d}$