Explanation:

- Option 1: President

- The President of India appoints the Speaker 'Pro tem' of the Lok Sabha.

- This appointment is generally for administering the oath to the new members and overseeing the election of the new Speaker.

- This is the correct answer.

- Option 2: Chief Election Commissioner

- The Chief Election Commissioner is responsible for administering elections and does not appoint the Speaker 'Pro tem'.

- Option 3: Chief Justice of Supreme Court

- The Chief Justice of India manages judicial appointments and matters, not parliamentary roles like the Speaker 'Pro tem'.

- Option 4: Prime Minister

- The Prime Minister plays a significant role in executive decisions but does not appoint the Speaker 'Pro tem'.