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

1. 1000 K
2. 10⁴ K
3. 10⁵ K
4. 10⁷ K

10⁷ K

Reason — Nuclear fusion is not possible at ordinary temperature and ordinary pressure because when two nuclei approach each other, due to their positive charge, the electrostatic force of repulsion becomes too strong between them that they do not fuse. Hence, to make the fusion possible, a high temperature of (approximately 10⁷ K) and high pressure is required. Due to thermal agitations both nuclei acquire sufficient kinetic energy at such a high temperature so as to overcome the force of repulsion between them when they approach each other and so they get fused.