It is implied in the passage that elective surgery and emergency surgery each come with some risk of death.
When the hospital stopped doing elective surgery for 5 weeks, mortality decreased during that period. After the 5 weeks, the hospital started doing elective surgeries again, and mortality went back up. This suggests that people were dying during elective surgeries.
Keep two things in mind. The author defines "elective" as a surgery that can be postponed. Also, the conclusion claims that some of the elective surgeries before the 5 week trial were unnecessary.
We need to need an answer choice that undermines the conclusion that the elective surgeries were attempted unnecessarily often.
Answer choice C would actually strengthen this conclusion. If hospitals in the area performed elective surgeries at a higher rate than in other places, that suggests that some of these surgeries could have been unnecessary.
Answer choice A is correct because it shows that these surgeries were truly necessary. A tells us that these surgeries, though elective, were meant to correct life-threatening issues. Just because they can be postponed, it does not make them unnecessary. Completing this surgeries as soon as possible actually makes them less risky than postponing them.