What is the main function of the circulatory system in multicellular organisms?

a) to bring oxygen into the lung

b) to put carbon dioxide into all blood vessels

c) to expel waste products from the body

d) to transport materials throughout the body

main function of the circulatory system in multicellular organisms is to circulate blood and oxygen in our body .so the right option is
A) to bring oxygen into the lung 
hope this helps

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.