Which of the following statements about the use of nuclear energy is true?
a. nuclear energy cannot be used safely.
b. nuclear fusion has no known useful applications.
c. nuclear fission is currently more useful for producing energy than nuclear fusion.
d. nuclear fusion has fewer safety risks than nuclear fission

D. Because nuclear fusion has no chain reaction involved.

In nuclear fission you basically shoot neutrons at heavy atoms, thus breaking them apart, which frees energy which can be used e.g. to heat water and produce electricity via a dynamo. But, and that is the point here, it also frees neutrons which again break others atoms, again freeing energy and neutrons and so on. Uncontrolled this chain reaction can produce enormous amounts of energy in a very short time. That’s basically what happens when a nuclear bomb is detonated or if a nuclear plant gets out of control.

In nuclear fusion, however, you have to have to push light atoms together e.g. with magnetic fields until they fuse together, which also frees energy. For energy to be freed, you have to keep up the pressure. If there is a malfunction and the magnetic fields collapse, the reaction simply stops. No chain reaction, no enormous amounts of energy, no catastrophe.

b would be the answer