Interpret this statement by David Morris: "The delicate balance between biology and culture, as it alters in a continuous flow, is what constitutes the elusive truth of illness."
a. Health practitioners don't have to update their knowledge.
b. Illness is easily understood and unrelated to cultural variables.
c. Health practitioners just have to know about biology to help patients.
d. People need to consider biological and cultural factors in order to try to understand illness.