Final answer:
Cancer is caused by mutations in abnormal cells due to carcinogens. Lifestyle choices such as smoking and unhealthy diet increase the risk of cancer, while sun exposure, excessive alcohol consumption, and tobacco use also increase the risk.
Step-by-step explanation:
Cancer is a group of diseases characterized by uncontrolled cell growth. It is caused by mutations in the DNA of abnormal cells, often triggered by carcinogens such as tobacco smoke, radiation, chemicals, or infectious agents. Lifestyle choices such as smoking, unhealthy diet, and lack of exercise are significant risk factors for cancer. In contrast, sun exposure, excessive alcohol consumption, and tobacco use actually increase the risk of developing cancer.