Mass is the amount of matter in any object. 
 
        
             
        
        
        
The correct answer is an accumulation of microorganisms in deep marine environments.
Chalk rock refers to a pure form of limestone produced in tropical and warm seas about 100 million years ago in the Cretaceous period. The microscopic marine algae known as coccoliths thrived in the ancient seas. Their shells were comprised of calcite. With the death of the algae, their bodies sunk to the floor of the sea and sediment of chalk got deposited.
Over many years layers of chalk sediment got deposited and resulted in compaction of loose sediment into solid chalk rock.
 
        
             
        
        
        
Answer:
in the explanation box
Explanation:
body's immune system trying to protect the wound from infection. The wound becomes red because blood vessels are opening so blood can bring oxygen and nutrients to the cut area, oxygen is needed for healing.
 
        
                    
             
        
        
        
<span>A gamete needs only half the number of chromosomes because two gametes join together hope his helps you
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Answer:
Explanation:
hepatic portal vein is a blood vessel that carries blood from the gastrointestinal tract and spleen to the liver. This blood are usually rich in nutrient because it contains extraction from digested materials or food substances in the gastrointestinal tract and it is processed in the liver for removal of toxins before the blood returns to the heart.