Final answer:
Light nuclei collide to form heavier nuclei during nuclear fusion, a process that releases significant energy and is essential to the operation of stars. Controlled fusion on Earth replicates conditions for energy generation with high safety and low environmental risks.
Step-by-step explanation:
The correct answer to this question is option (1): light nuclei collide to produce heavier nuclei. This process is known as nuclear fusion, and it is the reaction in which two or more lighter atomic nuclei come together to form a heavier nucleus. For instance, the fusion of hydrogen nuclei to form helium, which is the principal source of energy in the sun and other stars, releases vast amounts of energy.
For fusion reactions to occur, the reacting nuclei need to be brought extremely close to overcome the electrostatic repulsion between them, which requires very high temperatures. Controlled fusion on Earth aims to replicate these conditions to harness energy efficiently and with fewer risks compared to nuclear fission, which involves the splitting of heavy nuclei. Fusion has the potential to provide a nearly inexhaustible source of energy with minimal environmental impact.