Answer:
1. Vice President: Mike Pence.
Mike Pence is the Vice President of the United States, and would assume the role of President if something happens to the current president Donald J. Trump that will render him unavailable.
2. President Pro Tempore of the Senate: Chuck Grassley
The Pro Tempore takes over the role of the Vice President if the VP becomes unavailable (such as taking leave, or replacing the President in the event of National Emergency).
3. Secretary of State: Mike Pompeo
The Secretary of State oversees the US interest in the world, and handles all foreign affairs.
4. Speaker of the House: Nancy Pelosi
The Speaker of the House creates and uses an agenda as well as manage all debates and maintains order in the House.
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