Selective selection,since being smaller is an advantage the rabbits got smaller similar to evolution
        
                    
             
        
        
        
Answer:
The skull is from a fossil skull of Styracosaurus - a horned dinosaur.
Explanation:
This skull image is the skull of a Styracosaurus dinosaur who was a huge dinosaur almost 5 meters or more with the horned present on the skull. This is a fossil skull representation from the fossils.
Styracosaurus was present 75 million years ago during the Cretaceous period who was a completely herbivorous ceratopsian dinosaur. 
Thus, the skull is from a fossil skull of Styracosaurus - a horned dinosaur.
 
        
             
        
        
        
The answer is the first one because it doesn't create gases and, the third one doesn't even make any sense so its definitely not that one