A nurse is conducting a class on how to self-manage insulin regimens. A client asks how long a vial of insulin can be stored at room temperature before it 'goes bad.' What would be the nurse's best answer?

A If a vial of insulin will be used up within 21 days, it may be kept at room temperature.' B If a vial of insulin will be used up within 2 weeks, it may be kept at room temperature.' C If you are going to use up the vial within 1 month, it can be kept at room temperature.' D If a vial of insulin will be used up within 1 week, it may be kept at room temperature.'