sCiEntists ArE intErEstED in mArs BECAusE ______.
A．pEoplE might hAvE to migrAtE thErE somEDAy
B．pEoplE CoulD livE thErE nAturAlly
C．liFE hAs EvEr ExistED thErE
D．its AtmosphErE is quitE DiFFErEnt