I think the answer is Endospore. I'm sorry if I'm wrong...
        
             
        
        
        
You should have typed the question on Google instead of here
        
             
        
        
        
Answer: Single covalent bond in the long hydrocarbon chain.
Saturated fatty acids are long chains of hydrocarbon ( with single covalent bond) ending with the carboxylic group (-COOH). This means those fatty acids which possess only single bonds in their chemical structure are called as saturated fatty acids. They are densely packed, which makes them solid at room temperature.  
Example- Lauric acid ( present in coconut oil). It has 12 carbon atoms in its chemical structure.
 
        
                    
             
        
        
        
<h2>The answer is:</h2>
B) All organisms that cannot synthesize their food by means of photosynthesis or chemo synthesis are heterotrophic.
<h2>Explanation:</h2>
All  those organisms that cannot manufacture their own food and instead obtains its food and energy by taking in organic substances in the process of photosynthesis usually in the animals and plants. All animals, protozoans, fungi, and most bacteria are heterotrophs.