A nurse is reinforcing teaching with a client who has type 1 diabetes mellitus. Which of the following statements from the client indicates to the nurse the teaching is effective?

A. "I should inject the insulin into my abdominal area.": The abdomen provides the most consistent and predictable absorption for subcutaneous insulin, making it the preferred injection site for many patients. B. "I should increase my insulin when I exercise.": Exercise typically lowers blood glucose and increases insulin sensitivity, so blanket increases in insulin with exercise are usually not recommended without individualized guidance. C. "I will shake the insulin vial vigorously to mix.": Vigorous shaking can denature insulin proteins; for suspension insulins, gentle rolling end-to-end is recommended. D. "I will freeze unopened insulin vials.": Insulin must be refrigerated but should never be frozen - freezing damages insulin and makes it unusable.