The goal was to see if Earth's ecosystems could be successfully manufactured and maintained elsewhere in the galaxy, should we need to bail on this planet.
It was named Biosphere 2 because it was meant to be the second fully self-sufficient biosphere, after the Earth itself
        
             
        
        
        
The stomach is the correct answer it is lined with an digestive enzyme called pepsin.
        
             
        
        
        
I think D because the whole thing is gaseous and it has two atmospheric layers