A carcinogen is a substance capable of causing _______.

A carcinogen is a substance that has the potential to induce cancer. These agents can lead to changes in the DNA of cells, promoting uncontrolled cell growth and division, which ultimately can result in the formation of tumors. Understanding carcinogens is critical in health and safety contexts, especially in settings where exposure to hazardous substances is possible.

On the other hand, mutations refer to changes in the DNA that can be caused by various factors, not exclusively by carcinogens; thus, while some carcinogens may indeed cause mutations, this does not encompass the full definition of the term. Similarly, allergic reactions involve the immune system's response to certain substances, which is distinct from carcinogenicity. Lastly, infections are brought about by pathogens such as bacteria or viruses and are not directly associated with carcinogenic substances. Therefore, the connection between carcinogens and their role in causing cancer makes this the most accurate choice.