Explain why nuclear fusion requires very high temperatures.

Nuclear fusion requires very high temperatures to provide the necessary energy to overcome the electrostatic repulsion between the positively charged nuclei. At high temperatures, the kinetic energy of the nuclei increases, allowing them to collide with sufficient force to fuse together.

This question assesses the student's ability to explain the conditions necessary for nuclear fusion. It focuses on the relationship between temperature and the forces acting on atomic nuclei, which is crucial for understanding fusion processes in stars and potential energy sources on Earth.