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Answer:</h2>
The galaxies were classified based on the shape and structure exhibited by them.
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Explanation:</h2>
In the 1920's, the galaxies were classified based upon the shape and structure by famous scientist Edwin Hubble. He did it by a telescope with which he captured various galaxies existing. He ordered (or "arranged") their shapes as winding, banned winding, curved, sporadic, and impossible to miss. This framework was known as the Hubble morphological succession of cosmic system types.  
Hubble noticed that a few universes, similar to the M31-Andromeda Galaxy, showed up as circles and had arms of stars and residue which showed up in a winding example. Like M31, these worlds showed up almost uniform in splendor. Likewise, Hubble saw that in a portion of these sorts of worlds the arms were all the more firmly twisted around the cosmic system. He called these winding systems. Our Galaxy, the Milky Way, is a case of a winding universe.  
 
        
        
        
Answer:
This is an incomplete question. 
Below should be the complete one with options:
A researcher introduces a signal produced by bacteria to eukaryotic cells that she is culturing in the laboratory. Remarkably, she notices that this signal results in an increase in eukaryotic gene expression. How is this possible?
A.This gene expression is likely independent of the presence of the prokaryotic signal.
B.The signal is either similar in structure to a ligand used by eukaryotes, or this signaling pathway is utilized by both prokaryotes and eukaryotes.
C.This signaling pathway might actually be utilized by both prokaryotes and eukaryotes.
D.This signal is likely similar in structure to ligands utilized by eukaryotic cells.
E.This prokaryotic signal likely travels directly into eukaryotic cells and acts as a transcription factor.
THE CORRECT ANSWER IS B
B.The signal is either similar in structure to a ligand used by eukaryotes, or this signaling pathway is utilized by both prokaryotes and eukaryotes.
 
        
                    
             
        
        
        
Answer:
Which mussels... You did not list them. 
 
        
             
        
        
        
Kites most likely spent the majority of the time active perching because they were actively looking for prey from an arial angle which allowed them to scope out their next victim