Choose the INCORRECT statement

$\displaystyle \mathrm{CO}_2$ is the most acidic oxide among the dioxides of group of $\displaystyle 14$ elements.

Among the isotopes of carbon, $\displaystyle { }^{13} \mathrm{C}$ is a radioactive isotope.

Carbon exhibits negative oxidation states along with +$\displaystyle 4$ and +$\displaystyle 2$ .

Carbon cannot exceed its covalency more than four.