A nurse is planning to administer a controlled substance to a client who is experiencing pain. Which of the following actions should the nurse plan to take first?

The correct answer is B: Identify the client using two identifiers. This step is crucial for patient safety and medication administration accuracy. By confirming the client's identity using two identifiers (name, date of birth, or medical record number), the nurse ensures the right medication is given to the right patient. This initial verification step helps prevent medication errors and ensures the client's safety. Removing the medication from the cabinet, documenting administration, and comparing medication amounts are important steps but should follow the crucial step of confirming the client's identity to minimize the risk of error.