Christiaan Eijkman shared the Nobel Prize in 1929 for the discovery of vitamins. Eijkman went to Java to isolate the pathogen causing beriberi, an illness that appeared to be contagious as it was common in prisons and among ship crews. Eijkman noticed that chickens fed a diet of white rice also suffered from a similar disorder. When the chickens were fed a diet of red rice, the chickens quickly recovered. Eijkman returned to the Netherlands and persuaded a prison to feed the prisoners red rice, and the incidence of beriberi decreased. What would the next step for Eijkman be?

A. He can infer all prisoners should get the new diet right away.
B. He can infer that humans and chickens have very similar dietary needs.
C. He can infer that humans should eat a more varied diet.
D. He can infer that beriberi may be related to diet, but more and better studies are needed.