What’s the answer to this

B and D as well

Explanation:

All the electronic configuration of the elements of B end on s sub shell.

S energy level sub shell can hold 2 electrons and since Be, Mg, Ca Sr end in s.

We can say, they have same valence electrons, i.e 2 electrons.

Explanation:

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.