What causes Cancer?

Different cancers are related to different reasons. Reasons are not known for all cancers. However, there are certain risk factors, which frequently lead to cancer. Among the common factors Tobacco is most important. Nearly half of the cancers in India are due to tobacco.
Some common Risk factors for Cancer:
Tobacco:
Smoking: Cigarette, Bidi, Cigar, Hukka.
Smokeless: Zarda, Gutka, Khaini, Snuff, etc. in any form.
Alcohol : Increases effect of tobacco several times if a person is using both.
Infections – such as Hepatitis B (liver cancer), HPV (cervix, mouth) etc
Lifestyle – obesity (excess weight), high fat diet and lack of exercise are related to some common cancers like breast, prostate, colon.