A nurse is preparing to mix short-acting insulin with NPH insulin from two vials. Which of the following actions should the nurse take?

A. Ensuring the NPH insulin is drawn into the syringe first is correct. This prevents contamination of the short-acting insulin with NPH insulin, which could delay its action. B. Using two separate syringes is unnecessary; insulin can be mixed in one syringe. C. Administering the insulin within 20 min of preparation is not a requirement. However, insulin should generally be administered shortly after preparation to maintain effectiveness. D. Injecting air into the vial of short-acting insulin before drawing it is correct, but it should be done after the air is injected into the NPH vial.