Answer: The idiomatic expression that best completes the passage is B. cost an arm and leg.
Explanation: "Cost an arm and leg" is an idiomatic expression used to make reference to something that is very expensive and requires spending too much money. This idiom is related to the context of the sentence or the elements found before and after the blank space since the speaker is referring to medical attention, a hotel bill and large amounts of food. In other words, the speaker is talking about services that are not cheap at all; therefore, "cost an arm and leg" is the idiomatic expression that best completes the passage.
