Answer

1. Fusion 2. Fission 3. Both fusion and fission 4. Both fusion and fission 5. Fusion 6. Neither fusion nor fission

Explanation

Step1 The process of combining or merging light nuclei into heavier ones, releasing energy in the process, is known as fusion. This is a prevalent process in our sun and other stars. Step2 The process of fission, or the splitting of a large nucleus into two or more lighter ones, generates copious amounts of nuclear waste, often exhibiting dangerously high radioactivity. Step3 Both fusion and fission reactions have high activation energies, meaning a large amount of energy is required to initiate the reaction. Step4 Despite the high activation energies, great quantities of energy are released in both fusion and fission. This is why they are used as power sources in nuclear reactors and atomic bombs. Step5 Nuclear fusion serves as the main energy-producing mechanism in stars. Step6 Typically, neither fusion nor fission directly drives chemical plants. Operations in such plants mainly rely on non-nuclear chemical reactions.