Question

What did Fermi mean when he said, "The reaction is self-sustaining"?

The reaction reached critical mass.
A spontaneous chain reaction had been accomplished.
The nuclear reaction was out of control.
The nuclear reaction could be controlled and maintained.

Answer 1

The nuclear reaction could be controlled and maintained.

Step-by-step explanation:

People had initiated a self-sustaining nuclear reaction--and then stopped it. He had released the energy of the atom's nucleus and controlled that energy.

Fermi's achievement in setting off the first self-sustaining nuclear chain reaction from his design of an atomic pile led to a new Age of the Atom. The controlled release of nuclear energy was now a reality