How many of the following can be carcinogenic?

a. X-rays

b. Viruses

c. Gamma rays

d. Nicotine

e. UV rays

All the five are 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 (like nicotine) have been identified as a major cause of lung cancer. Certain viruses also cause cancer.