Final answer:
Steroids and other banned substances can enhance athletic performance, but they are illegal for nonmedical use and prohibited in sports due to health risks and ethical concerns.
Step-by-step explanation:
The correct response to the question 'What is true regarding steroids and other banned substances?' is c) They can enhance athletic performance but are prohibited in many sports. Performance-enhancing drugs, such as anabolic steroids, are known to potentially increase muscle mass, strength, and endurance, which can give athletes an unfair advantage in competition. However, these substances are illegal for nonmedical use and are banned by sports organizations due to ethical considerations, health risks, and the potential for serious side effects, including heart disease, liver damage, aggressive behavior, and infertility.