Answer :
The correct answer is carcinogen.
The substance that has the ability to cause cancer in normal cells is known as carcinogen. They promote carcinogenesis, the formation of cancer. Some examples of carcinogens are radioactive substances. some common examples which are not radioactive substances are certain dioxins and tobacco smoke. People generally think that carcinogens are synthetic substances or radioactive agents but this is not true. A carcinogen can be natural substances too. They are not toxins that can a person in no time but it is insidious to health.