Answer:
The main idea of the paragraph is best expressed in the sentence (4).
Step-by-step explanation:
From sentence (1) to (3), the narrator talks of the doctor and his basis of the illness of the people. These three sentences provide the context of the story or paragraph. But, sentence (4) is the epitome of the whole paragraph, providing the reasons of those health complains, and the understanding of the doctor of what to do. The last sentence provides the main idea of what the whole paragraph was talking about and the solution needed- that bodily functions are affected by spiritual and emotional phenomena as well as by physical influences, so it alone isn't always a health issue but more of the familial and emotional surrounding of the person.