Mars was once similar to earth in that

a.) it had only one moon
b.) liquid water flowed on its surface
c.) it showed evidence of plate tectonics
d.) its atmosphere had a thin layer of carbon dioxide

Ты не знаешь ни английского языка

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.