Answer:
D.  A mutation causing uncontrolled cell division
Explanation:
Cell division is controlled by various mechanisms. Any mutations in the genes regulating the cell division lead to uncontrolled cell division. Loss of control over the process of cell division leads to the formation of tumors.  
These tumors may cause cancer if they are transformed into malignant tumors. Hence, a mutation that causes loss of control over cell division is harmful.  
 
        
             
        
        
        
Titan's rivers, lakes, and seas of liquid methane and ethane could provide a habitable environment on the moon's surface, though any life there would most likely be very different from life on Earth.
Methane gas is effective at trapping heat and burns quickly. As a result, methane is one of the most important human fuels. Furthermore, methane in the atmosphere helps to regulate the Earth's climate.
Over the first 20 years after it enters the atmosphere, methane has more than 80 times the warming power of carbon dioxide. Even though CO2 has a longer lasting effect, methane drives warming in the short term. Methane from human activity is responsible for at least 25% of today's global warming.
As a result, methane not only contributes to global warming directly, but also indirectly through the release of carbon dioxide.
To learn more about importance of methane cycle, here
brainly.com/question/2626091
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Energy flows through an ecosystem and cannot be recycled. 
        
             
        
        
        
The correct answer is:
Plants close their stomata during times of intense heat or drought in order to prevent water loss and maintain homeostasis.
Explanation:
Guard cells tend to open stomata within the day when there are lots of day and close stomata at night when the sun is not present and photosynthesis is not happening. They will also close stomata if the air is dry or hot, which minimizes water waste indoors evaporation.
 
        
                    
             
        
        
        
The best description about the brain stem is: it is the most important organ of our body's survival. It connects the brain and the spinal cord, controls the vital organs like the lungs and heart and it also coordinates the many essential body reflexes.