Answer:
D/ Kilograms per cubic-centimeter
 
        
                    
             
        
        
        
Answer:
Actin filaments return to their original positions (does not occur in muscle contraction, according to the sliding filament model).
Explanation:
 
        
             
        
        
        
Answer:b) The air at high altitudes are less dense, so its harder to breathe.
Explanation:
AS altitude increases, the air pressure drops. This reduces the amount of gas molecules in the air so the air becomes less dense compared to air closer to sea level.
 
        
                    
             
        
        
        
Answer:
hemotrophs are organisms that obtain energy by the oxidation of electron donors in their environment. Chemoautotrophs use inorganic energy sources to synthesize organic compounds from carbon dioxide. Chemoheterotrophs are unable to utilize carbon dioxide to form their own organic compounds.
Explanation: