nAsA is mAking rEsEArCh on vArious kinDs oF spACE hABitAts BECAusE ______.
A．pEoplE on thE EArth must All movE to thE moon
B．mAny spACE inDustriEs will nEED workErs to work out in spACE
C．nEw mArkEts AnD morE joBs will BE CrEAtED By spACE inDustriAlizAtion
D．spACE rEsEArCh hAs rEAChED A nEw lEvEl