A client receives the wrong medication in error. The nurse who made the medication error should do which of the following first?

The correct answer is A: Observe the client. The nurse should first assess the client for any adverse effects from the wrong medication. This is crucial to ensure the client's safety and well-being. Completing an incident report (choice B) should come after ensuring the client's immediate needs are addressed. Notifying the nurse manager (choice C) and calling the client's provider (choice D) can be done after assessing the client. The priority is to monitor the client's condition and take appropriate action to mitigate any harm.