The President, who heads the executive branch of the US government, appoints the ambassadors. The Senate must approve his choices.
Senate
Yes they can!
Yes, whenever the President makes an appointment to any form of Government the Legislative Branch (House of Representatives and the Senate) can approve or deny his appointments.
The Senate (legislative branch) must confirm (approve) these appointments by the President. Thus the power to appoint is divided
The Senate
Nobody, Supreme Court judges are not elected they are appointed by the President. Then the Senate must approve the appointment before he can actually take office as a judge.
The Congress.
The Senate
Congress must approve all appointments of ambassadors == ==
The appointment of executive branch official must approved by the Senate. These include cabinet appointments and ambassadors. The US Constitution requires this interaction.
Congress, and the senate to be specific, but im not sure