Answer: conservative model 
Explanation: DNA isolated after one generation produced a single band which was a higher and intermediate in density between the heavy and light Nitrogen isotopic DNA used, showing that the first generation was a hybrid DNA. This observation fit with the dispersive and semi-conservative models only. And so at this generation, the conservative model was discarded.
 
        
                    
             
        
        
        
D) Vaccines work to fight the disease 
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As you can see in the picture presented below, the three classes of water have distinctive traits.
Pure substances contain only one element, they are not mixtures of different things.
The homogeneous mixtures have multiple elements, but they are so well blended together that you can't easily observe or separate them.
In heterogeneous mixtures, we can easily differentiate between different elements of the mixture.
 
        
        
        
Answer: Mallets 
Why? (Little confused by question but this is what I know about metal and bamboo instruments) 
You have to play the with a mallet that is less dense and less hard than the material you play on like metal and bamboo
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Yes, our distance from nature and our chronic immunological discontent could be related. Nature may be the cause of allergic problems.
<h3>What is an allergy?</h3>
Allergy is a common immune response produced by certain substances that alter the stability of the immune system.
Allergy may be caused by different materials present in nature that alter our immune system.
For example, pollen grains may cause allergic responses such as inflammation and thus produce chronic immunological problems.
Learn more about allergies here:
brainly.com/question/2681615