Around four hundred million years after the formation of earth, the planet's atmosphere would have been almost entirely a. argon b. oxygen c. nitrogen d. carbon dioxide

passing a magnet thought the

mixture , because iron gets attracted to magnet .

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.

a:

by the combination of an unlimited number of elements