What two factors convinced Emperor Hirohito to surrender to the U. S. unconditionally?

a.) the capture of Iwo Jima and the firebombing of Tokyo

b.) The U. S. concession that he would remain in power and the fear of the atomic bomb

c.) the use of the atomic bomb on Japan and the Soviets entering the war

d.) the immense casualties of the war and the loss of public support