Thymine, Guamine, cytosine, and atanine make up the steps in dna (the nitrogenous bases) but the sided are a patter of phosphate then sugar.
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Answer:
D
Explanation:
The atmosphere is not an eycosystem
 
        
             
        
        
        
Answer:
Soil erosion. 
Explanation:
No-till plowing can be defined as a farming method or technique which typically involves planting crops (seedlings) without tilling the soil rather the farmer would only open a narrow or very shallow trench of sufficient depth and width to cover up the seedlings. Thus, the no-till plowing makes crop residues to be left on the soil and by extension preventing soil erosion through the absorption of water by the crop residues. 
Hence, by leaving crop roots in the ground and stalks on the surface, no-till plowing helps prevent soil erosion.
Additionally, the water retention ability of no-till plowing is usually a boon to farmers because it slows down evaporation and serves as a good protection for drought-stricken environments.