<span>A stem is one of two main structural axes of a vascular plant, the other being the root. The stem is normally divided into nodes and internodes. The nodes hold buds which grow into one or more leaves, conifer cones, roots, other stems, or flowers (inflorescences); the internodes distance one node from another.</span>
        
                    
             
        
        
        
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The enzyme responsible for separating the two strands of DNA in a helix so that they can be copied during DNA replication.Explanation:
 
        
             
        
        
        
Answer:
A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world.
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Composed of a phospholipid bilayer.
Hydrophilic heads and lipophilic tails on the phospholipids.