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. Inject air into the vial to withdraw the short-acting insulin is the correct procedure. The nurse should first inject air into the NPH vial without drawing up any insulin, then inject air into the short-acting insulin vial and withdraw the required dose. This prevents contamination of the short-acting insulin with NPH insulin. B. Ensure the NPH insulin is drawn into the syringe first is incorrect. The short-acting insulin should be drawn into the syringe first to avoid contaminating it with NPH insulin. C. Use two separate syringes to mix the insulin is not necessary. Insulin can be mixed in one syringe as long as the correct procedure is followed. D. Administer the insulin within 20 minutes of preparing it is not specific to the mixing procedure. Insulin should generally be administered promptly after preparation, but the exact timing can vary.