The temperature required for the process of nuclear fusion is nearly:

1. 1000 K
2. 10⁴ K
3. 10⁵ K
4. 10⁷ K

(a) Name the process, nuclear fission or nuclear fusion, in which the energy released per unit mass is more?

(b) Name the process, fission or fusion which is possible at ordinary temperature.

What is the source of energy of sun or stars?