Which statement describes one way that nuclear fission differs from nuclear fusion? A. Nuclear fission can be sustained only in the Sun and other stars.

B. Nuclear fission can occur spontaneously.

C. The temperature required for nuclear fission is more than 15 million degrees Celsius.

D. It is more difficult to start and control nuclear fission,​

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.