Which of the following polymers has the empirical formula identical with that of its monomer?

${\mathrm{nCF}}_2={\mathrm{CF}}_2\underset{\mathrm{Highpressure}}{\overset{\mathrm{Catalyst}}{\to }}\underset{\mathrm{Teflon}}{{[-{\mathrm{CF}}_2-{\mathrm{CF}}_2-]}_{\mathrm{n}}}$

It is an addition polymer of carbon tetraflouride.

∵ The shift forming a chain in addition polymer, the empirical formula remains the same.