Concept:The sentence needs a logical swap between two words to make it meaningful.
Explanation:The original sentence is: "The patient knew that the doctor trusted what he was doing..."
This is incorrect because a patient should trust the doctor, not the other way around.
So the words at positions (A) and (B) must be interchanged.
After swapping, the sentence becomes: "The patient trusted that the doctor knew what he was doing and agreed to undergo the risky surgery."
This corrected version is logical and clear.
Thus, the required rearrangement is A-B.
This corresponds to option C in the list.
Answer:Option C (A-B)