Which among the following is a cause of cancer ?

The correct answer is Option (4) → All of these.

Transformation of normal cells into cancerous neoplastic cells may be induced by physical, chemical or biological agents. These agents are called carcinogens. Ionising radiations like X-rays and gamma rays and non-ionizing radiations like UV cause DNA damage leading to neoplastic transformation. The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer.

All the options listed are known causes of cancer:

• Heavy smoking – Linked to lung cancer and several other types.
• Betel and tobacco chewing – Strongly associated with oral and esophageal cancers.
• Excessive exposure to ultraviolet (UV) rays – Increases the risk of skin cancer, including melanoma.

So, all of these are carcinogenic factors