The president-this is another poorly written question. the justices are not appointed directly, it is a complex process that involves both the president and the senate.
i marked president as the correct answer, since that is where the nomination originates. then the senate either consents or rejects the nomination.
power to nominate the justices is vested in the president of the united states and appointments are made with the advice and consent of the senate. article iii, �1, of the constitution further provides that [t]he judges, both of the supreme and inferior courts, shall hold their offices during good behavior, and shall, at stated times, receive for their services, a compensation, which shall not be diminished during their continuance in office.