Final answer:
Senators in Canada are appointed by the Governor General on the advice of the Prime Minister. In the US, as per Amendment XVII, Senators are directly elected by voters of each state. Supreme Court justices in the US are nominated by the President and confirmed by the Senate.
Step-by-step explanation:
Senators in various systems are chosen through different methods. Highlighting a few will help clarify the process of appointment in various countries.
In Canada, Senators are appointed by the Governor General, but they are selected on the advice of the Prime Minister.
Similarly, in the United States, the Amendment XVII to the Constitution enabled direct election of Senators by the voters of each state, whereas previously, they were chosen by state legislatures.
When it comes to appointing Supreme Court justices, including in the United States, the President nominates them and with the advice and consent of the Senate, they are appointed.