The correct answer is the fourth option. The nervous system is the system in the body which can be affected by ionizing radiation. Exposure to this kind of radiation may lead to changes in motor function or neurological disorders.
The right answer is noble gases.
The noble gases, or rare gases, are the chemical elements of group 18 (formerly "group VIIIA" or even "group 0") of the periodic table. These are helium He, neon 10Ne, argon 18Ar, krypton 36Kr, xenon 54Xe and radon 86Rn, the latter being radioactive.
This property means that they can not bind with other atoms to form molecules or lose electrons to transform into ions, hence their name noble or inert gases (they are not very active and do not do not mix). In nature, all elements "want" to become stable.
Answer:the CO2 molecule has an excess of electron
