I believe its Uranus and Neptune, please tell me if I'm wrong. 
Reason: an ice planet is made up of a semi icy surface like perhaps water, oxygen, or any other element stronger than hydrogen. Neptune and Uranus both meet this match, they are made up of elements that are actually stronger than hydrogen.
 
        
             
        
        
        
Question:why were maggots there only after the flies left
Hypotheses:the maggots are fly larva
        
                    
             
        
        
        
The best answer to fill in the blank is "multilayered membrane."
        
             
        
        
        
The brain stem is the answer that you are looking for
        
                    
             
        
        
        
The jet stream flows west to east