Provided that there's no diagram, most molecules have particular areas on the molecules, called the "active area" that act as a lock to a particular substrate's molecular structure, providing the key. 
An enzyme's active area is only able to be "unlocked" by a certain substrate's "key". 
        
                    
             
        
        
        
Answer:
Organelle (oppitional, I don't put this on my paper but you can if you want), cells, tissues,  
Explanation:
 
        
             
        
        
        
Mitosis is cell division in to daughter cells with the same chromosome number as the parent cell
        
             
        
        
        
Human migration is the movement over long distances, movement from one country/region  to another ) by people . Humans moved because of the c<span>hanging climate and landscape and inadequate food supply. </span>The first human movement was t<span>he movement of </span>Homo erectus<span> out of Africa across </span>Eurasia<span> about 1.75 million years ago. </span> 
Than industrialization<span> encouraged migration wherever it appeared.
Wars also created migration. (</span><span>The First and Second World Wars, and wars, genocides, and crises sparked by them, lead to migrations).</span>
        
             
        
        
        
Answer:
The correct answer is option d) nutrients absorption.
Explanation:
The stomach has several important functions.  Mechanically digestion involves the contraction of muscles of the stomach and churning of the food to enhance digestion. The secretion of HCl and enzymes is an important role of the stomach for digestion.
Nutrient absorption is a major function of the intestine specifically small intestine for nutrient absorption.
Thus, the correct answer is d) nutrients absorption.