Task: Explanation
Input (English): Question: African Americans have darker skin than other Americans. Researchers were not surprised to discover therefore, that vitamin D insufficiency among African Americans is _____ than among other Americans? 
 Answer: more prevalent
Output (English): Pigments in the skin act like a filter that can prevent the skin from making vitamin D. As a result, people with darker skin need more time in the sun than people with lighter skin to make the same amount of vitamin D.