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.
Caucasian Americans have lighter skin than other Americans. Researchers were not surprised to discover therefore, that vitamin D insufficiency among Caucasian Americans is _____ than among other Americans?

A) more prevalent
B) less prevalent