**Core Concept:** Thorium is a radioactive element that can cause radioactive poisoning when ingested or inhaled, ultimately leading to various health complications including cancer. It is a member of the actinide series and has the atomic number 90.

**Why the Correct Answer is Right:** Thorium-induced tumors occur due to the radioactive decay of thorium, which releases alpha particles. These alpha particles can damage the DNA within cells, leading to mutations and ultimately cancer development. When thorium is absorbed into the body, it accumulates primarily in the bones, lungs, and kidneys, as these tissues have a high turnover rate and can retain radioactive substances over time.

**Why Each Wrong Option is Incorrect:**

A. **Option A:** Uranium-induced tumors (atomic number 92) are incorrect because uranium is not as commonly associated with thorium and does not have similar properties.

B. **Option B:** Protactinium-induced tumors (atomic number 91) are incorrect because protactinium is another radioactive element, but its properties and the associated risks are different from thorium.

C. **Option C:** Carbon-induced tumors are incorrect because carbon has an atomic number of 6 and is not radioactive. Carbon-induced tumors would not be associated with radioactive decay or the risks associated with thorium.

D. **Option D:** Radium-induced tumors (atomic number 62) are incorrect because radium is a radioactive element with similar properties to thorium, but thorium is specifically mentioned in the question. Thorium-induced tumors are the correct answer.

**Clinical Pearl:** Thorium poisoning, though rare, highlights the importance of radiation safety protocols in industries and research settings where thorium is used. Thorium exposure can be prevented by proper handling, storage, and disposal of thorium-containing materials. In case of exposure, prompt medical attention and treatment are essential to minimize the risks of radioactive poisoning and its associated health complications.