Biological soil crusts<span> are communities of living organisms on the </span>soil<span> surface in arid and semi-arid ecosystems. They are found throughout the world with varying species composition and cover depending on topography, </span>soil<span> characteristics, climate, plant community, microhabitats, and disturbance regimes.</span>
        
             
        
        
        
Answer; B
they're bones allow them to lift them up in the sky.
        
             
        
        
        
Answer:
contraction and relaxation of the heart
Explanation: