Answer:
Changes that cannot be reversed are called irreversible changes
Example: if you cook an egg or if something goes bad. these changes can not be reversed.  
 
        
             
        
        
        
Answer:
Spindle fibers form a protein structure that divides the genetic material in a cell. The spindle is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both types of nuclear division: mitosis and meiosis. During mitosis, the spindle fibers are called the mitotic spindle.
Explanation:
 
        
                    
             
        
        
        
Answer:
The water we drink now was the same water the dinosaurs drank. Discuss how the water cycle makes this statement accurate. Include different parts of the water cycle and what processes help move the water through each part.
 
        
             
        
        
        
I belive that the emperor penguin fits all the criteria of Group B.
 
        
             
        
        
        
C black holes because we wouldn't be here right now if there were