Adeficiency of what vitamin produces a characteristic cracking and redness at the corners of the mouth? a. biotin b. niacin c. riboflavin d. ascorbic acid

A deficiency of Riboflavin vitamin produces a characteristic cracking and redness at the corners of the mouth.  Other symptoms include sore throat, swelling of the lining of the mouth and throat, cracks or sores on the outsides of the lips and the corners of the mouth, inflammation and redness of the tongue and a moist, scaly skin inflammation. Riboflavin or B2 is found in food and  is used as a dietary supplement. 

They include lobsters and crabs