31. which branch of physics studies the risks and benefits of nuclear power?\nmagnetism\nradioactivity\ntherm…

Brief Explanations:

Radioactivity deals with the properties and effects of radioactive substances, which is closely related to nuclear power. Magnetism focuses on magnetic fields and materials. Thermodynamics is about heat, work, and energy conversion. Modern physics encompasses a wide - range of topics like relativity and quantum mechanics but is not specifically about nuclear power risks and benefits like radioactivity.

Answer:

radioactivity