A nurse is reinforcing teaching with a client who has a prescription for ferrous sulfate elixir. Which of the following statements by the client indicates an understanding of the teaching?

"I can prevent nausea if I take the medication on an empty stomach."

"I can prevent constipation if I drink more milk while taking this medication."

"I will report black stools to my doctor."

"I will mix the medication with a full glass of water."