The correct answer is b. Release of short-chain fatty acids.
The intestinal microflora is complex ecosystem which contains over 400 bacterial species.That microflora is  capable of fermenting indigestible carbohydrates (dietary fiber) to short-chain fatty acids such as acetate, propionate, and butyrate.
 
        
             
        
        
        
 C. transporting nutrients to cells
        
             
        
        
        
The answer is d to the question!!!
        
             
        
        
        
Ecologists are the persons who study the interrelationships between organisms and their environments. Like they research upon the species found in forests or deserts interact with each other and as well as their surroundings. 
They test whether a species is occupying its complete fundamental niche or only a portion of it by observing if the species are expanding their range after the removal of a competitor because two species with the same fundamental niche will exclude other competing species.