Question

why are very high temperatures and pressures required for fusion to occur?
o to generate the neutrons that are needed to break the nuclei
o to overcome the repulsion between the protons in the nuclei that join
o to maintain the proper conditions to keep the chain reaction going
o to keep the uranium fuel separate from the control rods

Explanation:

In nuclear fusion, nuclei (which have positively - charged protons) need to come close enough to fuse. Due to the electrostatic repulsion (Coulomb's law) between like - charged protons in different nuclei, high temperatures (to give nuclei high kinetic energies) and high pressures (to force them close) are required to overcome this repulsion.

• The first option is incorrect because neutrons are not generated in the way described for fusion to break nuclei. Fusion is about combining nuclei, not breaking them (that's fission).
• The third option is about chain reactions which are characteristic of fission, not fusion.
• The fourth option is related to fission reactor components (uranium fuel and control rods) and has nothing to do with the requirements for fusion.

Answer:

to overcome the repulsion between the protons in the nuclei that join