Correct Option: C

Argon is the third most common gas in the Earth’s atmosphere, at 0.93% (9,300 ppm), making it approximately 23.8 times as abundant as next most common atmospheric gas, carbon dioxide (390 ppm), and more than 500 times as abundant as the next most common noble gas, neon (18 ppm). Nearly all of this argon is radiogenic argon-40 derived from the decay of potassium-40 in the Earth’s crust. In the universe, argon-36 is by far the most common argon isotope, being the preferred argon isotope produced by stellar nucleosynthesis in supernovas. We find the inert gases argon (9,340 ppmv), neon (18.18 ppmv) and helium (5.24 ppmv) in the earth’s atmosphere. Note that we use ppmv here to mean parts per million by volume.Argon is produced industrially by the fractional distillation of liquid air. Argon is mostly used as an inert shielding gas in welding and other hightemperature industrial processes where ordinarily non-reactive substances become reactive.