The answer is option B: The U.S. Constitution assigns the Executive Branch the power of appointing federal judges.
The power of the Executive Branch is vested in the President of the United States. In Article II, Section 2, Clause 2: Treaties, International Agreements, Appointments and Congressional Regulation of Offices is stated some of the President's duties and powers, including to appoint the federal judges. Here is an excerpt of the mentioned article that supports the answer:
"...and he (the president) shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments."
