The answer that fits the blank provided above is STEROIDS. Steroids are fat-soluble signal molecules. This is one of the derivative compounds of cholesterol along with Vitamin D and bile salts. All steroid hormones are considered as a derivative of cholesterol. The answer for this would be option D.
        
                    
             
        
        
        
The answer could be any of the following:
* energy
* sugar
* carbohydrates
* (possibly even) food. 
        
             
        
        
        
Answer:
1) To form a multicellular organism, a zygote must divide into 16 cells which produces ball structure called a morula. After that, morula is converted into a structure called blastula. 
2) Adult stem cells are responsible for the maintenance of tissues and repair the damage tissues in the body. It is also called somatic stem tissue. It increase in number through cell division. 
 
        
             
        
        
        
its Falseeeeeeeeeeeeeeeeeeeeeeeeeeeee
 
        
                    
             
        
        
        
Both are hard structures that reduce erosion causes by waves.