কোনটি আইসোটোন-এর উদাহরণ?

$_{18}^{40}\mathrm{Ar},~_{19}^{40}\mathrm{K},~_{20}^{40}\mathrm{Ca}$

$_{16}^{36}\mathrm{S},~_{17}^{37}\mathrm{Cl},~_{19}^{39}\mathrm{K}$

$_{20}^{39}\mathrm{Ca},~_{20}^{40}\mathrm{Ca},~_{20}^{41}\mathrm{Ca}$

$_{19}^{40}\mathrm{K},~_{20}^{40}\mathrm{Ca},~_{21}^{39}\mathrm{Sc}$