18 Elements D and E are both in Period 3. Element D has the smallest atomic radius in Period 3. There are only two elements in Period 3 which have a lower melting point than element E.
Elements D and E react together to form compound L.
Which compound could be L?
B Mgs
C Nas
D PC13
A MgCl2

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.

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its first and third is your answer i did the qustion the fourth isnt right