Which of the following substances is not classified as a carcinogen?

Vitamin C is not classified as a carcinogen, which means it does not have properties that are known to cause cancer in humans. In fact, Vitamin C is considered an antioxidant and plays a protective role in the body by combating free radicals, which can contribute to cell damage and potentially lead to cancer development.

In contrast, tobacco smoke, formaldehyde, and asbestos are recognized carcinogens. Tobacco smoke contains a number of harmful chemicals that can lead to various types of cancer, including lung cancer. Formaldehyde is a substance used in various industrial applications and has been linked to nasopharyngeal cancer and leukemia. Asbestos is a mineral fiber that has been associated with lung cancer and mesothelioma, a specific type of cancer affecting the lining of the lungs.

Thus, identifying substances that promote or contribute to cancer is crucial, and Vitamin C stands out as a non-carcinogenic substance in this context.