(i) Tobacco is obtained from the tobacco plant Nicotiana tobaccum and Nicotiana rustica.
(ii) The dried and cured leaves of its young branches make the commercial tobacco used worldwide.

Cancer causing agents are called carcinogens. They are physical, chemical agents, ionizing radiations and biological agents.
(i) Physical Irritant: Heavy smoking causes lung cancer and cancers of oral cavity, pharynx (throat) and larynx. Betel and tobacco chewing causes oral cancer. Excessive exposure to sunlight may cause skin cancer.
(ii) Chemical agents: Nicotine, caffeine, products of combustion of coal and oil, pesticides, asbestos, nickel, certain dyes, and artificial sweeteners induce cancer.
(iii) Radiations: Ionizing radiations like X-rays, gamma-rays, radioactive substances and non-ionising radiations like UV rays cause DNA damage leading to cancer.
(iv) Biological agents: Cancer causing viruses are called oncogenic viruses.

Insulin deficiency occurs due to destruction of \(\beta \)-cells of the pancreas.

(i) The cancerous cells migrate to distant parts of the body and affect new tissues.
(ii) This process is called metastasis.

Obesity is due to genetic factors, physical inactivity, eating habits (overeating) and endocrine factors.

Psychotropic drugs acts on the brain and alters the behaviour, consciousness, power of thinking and perception.

(i) For diabetic patients, the food to be avoided are:
a. Refined sugars (sucrose and glucose).
b. Saturated fat intake should be reduced.
These food release sugars rapidly in the blood stream.
(ii) The food to be included in diabetic patients are:
a. Flax seeds containing insoluble fiber, Guavas, Tomatoes and Spinach.
b. Diet comprising whole grains, millets (jowar, bajra, ragi), green leafy vegetables, wheat and unpolished rice should be included in diet regularly. These foods help reduce blood sugar levels.

(i) Diet Management: 
a) Reduction in the intake of calories, low saturated fat, and cholesterol rich food, low carbohydrates, and common salt are some of the dietary modifications.
b) Diet rich in polyunsaturated fatty acids (PUFA) is essential.
c) Increase in the intake of fiber diet, fruits, and vegetables, protein, minerals, and vitamins are required.
(ii) Physical activity:
Regular exercise, walking, and yoga are essential for body weight maintenance.
(iii) Addictive substance avoidance:
Alcohol consumption and smoking are to be avoided.

HIV is transmitted generally by
(i) Sexual contact with infected person.
(ii) Use of contaminated needles or syringes especially in case of intravenous drug abusers.
(iii) By transfusion of contaminated/infected blood or blood products.
(iv) From infected mother to her child through the placenta.

(i) Atherosclerosis is a disease in which plaque builds up inside your arteries.
(ii) Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood.
(iii) Over time, plaque hardens and narrows your arteries.
(iv) It leads to ischemia (deficient blood supply to heart muscle) and myocardial infarction (death of the heart muscle tissue).