Should there be a(n) leaving the president, vice president, speaker of the house, and president pro tempore unable to assume the duties of the president, the cabinet represents

a.
catastrophe . . the presidential order of succession
b.
security threat . . the body that appoints a new president to office
c.
catastrophe . . the office of the president until a new president is elected
d.
security threat . . the supreme authority in government until the threat is eliminated