Final answer:
Radioactive substances such as uranium, thorium, radon, and radium are unstable and emit radiation as they decay. These substances are known for their natural occurrence and their use in various applications including medical and energy sectors. The correct answer to the question is e. All of the above.
Step-by-step explanation:
The question asks which of the listed substances are examples of radioactive substances. Radioactive substances are materials that contain unstable isotopes which emit radiation as they decay. The most common types of radiation are alpha particles, beta particles, and gamma rays. Uranium, thorium, radon, and radium are examples of naturally occurring radioactive elements and are known for undergoing radioactive decay by emitting these types of radiation.
Answering the provided question, among the substances listed:
- Uranium is a well-known radioactive element that undergoes alpha decay.
- Thorium is another radioactive element that can decay by emitting alpha particles.
- Radon is a hazardous radioactive gas that is a decay product of uranium and thorium.
- Radium is a radioactive element that was discovered by Marie and Pierre Curie and also emits alpha particles during its decay.
Based on this information, the answer to the question is e. All of the above.