A nurse receives a new prescription over the telephone from a client's provider. Which of the following actions should the nurse take first?

The correct answer is A: Write down the complete prescription. This is the first action the nurse should take to ensure accurate documentation and prevent errors. By writing down the complete prescription, the nurse can verify the details with the provider, confirm any unclear information, and have a record for future reference. Reading back the prescription (B) is important but comes after writing it down. Documenting the prescription (C) and ensuring the provider signs it (D) are important steps but should follow the initial action of writing down the prescription.