Which of the following restrictions apply when a non-licensed person is allowed to speak to a foreign station using a station under the control of a licensed amateur operator?

Allowing an unlicensed person to speak over your amateur radio station constitutes "third-party communications." Because international treaties govern amateur radio, you can only pass third-party traffic to a foreign country if the United States has a formal third-party agreement with that specific country's government. While the licensed control operator is always responsible for the station, the non-licensed person actually is allowed to speak the station identification over the air, as long as it is done under the control operator's direct supervision. Additionally, there is no U.S. citizenship requirement for the unlicensed person speaking into the microphone, which makes the third-party agreement the only valid restriction listed.