A student was asked to determine the activity of four unknown metals, W, X,Y, and Z.

c is the answer because when something is left after something evaporates that shows the chemical change.

sup bro, im dumb, but this is what i found xd

"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"