【C10】A．empowersB．reinforcesC．supportsD．sustains

To determine that a compartment contains sufficient oxygen to sustain life, you should use

【C10】A．buildB．destroyC．conserveD．sustain

These seats are ____ for special guests.A.preservedB.reservedC.retainedD.sustained

How should we understand the social benefits of a sustainable transportation system？A．It s

【C10】A．retainingB．containingC．obtainingD．sustaining

56._________A. strategies B. reasonsC. supportsD.