Ans.
Carcinogens can be defined as a physical and chemical agent that leads to development of cancer (carcinogenesis), such as radiation, toxic chemicals, and tumor-causing viruses due to mutations in genetic material of cells.
Tobacco is considered as a carcinogen as it can cause lung cancer, mouth cancer, and various other types of cancer. Tobacco contains around seventy chemicals, which promote or initiate cancer and make it a potent carcinogen.
Thus, the correct answer is option). 'it causes mutations leading to cancer.'