Answer: D
bcuz i said so and this
        
                    
             
        
        
        
The answer here is D, and it's kind of obvious. But you probably already knew the answer and are just doing this for piece of mind.
Explanation: Just the fact that we don't know whether or not there even is extraterrestrial life rules out every other answer, without even needing to go in depth.
(Okay, I read your question completely wrong, it's asking for which one of these has been solved isn't it?)
This is tough because all of these other than D have been figured out. Go with the methane atmosphere then.
 
        
             
        
        
        
<u>Answer:</u>
<em>Colchicine is also known as mitotic poison. When it is added the separation of chromosomes of daughter cells are stopped. </em>
<u>Explanation:</u>
This is because the formation of spindle fiber is not allowed in the mitosis phase. Basically it is the process of arresting the mitosis at metaphase to study the chromosomes properly. 
The addition of colchicine prevents the chromosomes to move to opposite poles. It makes the cell polyploidy. Hence the of addition of colchicine is the polyploidy of the cell.
 
        
             
        
        
        
Halophiles are extremophiles that thrive in environments with very high concentrations of salt. <span>Halophiles prevent this loss of water by increasing the internal osmolarity of the cell by accumulating </span>osmoprotectants<span> or by the selective uptake of potassium ions. Hope this helps.</span>
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