Explain complementary base pairing. which are purines and pyrimidines and who bonds to whom? how many hydrogen bonds form between them?

Each nitrogenous base has one counterpart. The purines are adenine and guanine and they pair with the pyrimidines thymine and cytosine, respectively. There are two hydrogen bonds between adenine and thymine and three hydrogen bonds between guanine and cytosine. 

The answer is atmosphere. there are four spheres of the earth: 1. geosphere (from greek word 'geo' = ground), 2. hydrosphere (from greek word 'hydro' = water), 3. biosphere (from greek word 'bio' = life), and 4. atmosphere (from greek word 'atmo' = air). a magnetosphere is a region of space around astronomical objects controlled by the magnetic field of that object. through the process of elimination, since lightning is present in the air, it can be found in the atmosphere.