whEthEr thErE is suFFiCiEnt nitrogEn on mArs is importAnt BECAusE it ______.
A．CAn rAisE thE tEmpErAturE oF mArs
B．CAn protECt living BEings From hArmFul rAys
C．CAn ChAngE thE AtmosphErE oF mArs
D．is An importAnt pArt oF thE Air pEoplE BrEAthE