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.
 
        
                    
             
        
        
        
Basement membranes are thin, dense sheets of specialized, self- assembled extracellular matrix that surround most animal tissues. The basement membrane is a fibrous matrix composed primarily of glycoproteins, type IV collagen, and laminin that are secreted by the epithelial cells.
        
             
        
        
        
Answer: 12 per cent 
Explanation:
The REM sleep is associated with the prolonged erections males and  pelvic thrusting in the females.
It is not being pursued for further studies as a concern of the function of REM sleep. The Yu and Fu found that the sleep involves the dreams about sexual activity.
The desires and fantasy of the real life appears to be complete in the dreams and 12 per cent of the total population see these dreams.
 
        
             
        
        
        
12 or 13 mostly 12 though