Emphysema is a form of chronic lung disease, usually caused by smoking.
Bronchitis is caused by tobacco smoke, dust, fumes, vapors and air pollution.
Gastric and duodenal ulcers that occur in the stomach are called as gastric ulcers. Ulcers that occur in the upper area of small intestine, which is the duodenal ulcers.
Therefore, the correct answer is option D.

Nicotine is a potent parasympathomimetic alkaloid and a stimulant drug. In particular, it is both a stimulant and a relaxant. It causes a release of glucose from the liver and adrenaline from the adrenal medulla thereby causing stimulation of nerve impulses and muscle relaxation.
Nicotine also produces adverse fetal effects. It is likely that hypoxia, undernourishment of the fetus and direct vasoconstrictor effects on the placental and umbilical vessels play a role.
Therefore, the correct answer is option D.

Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath due to over-inflation of the alveoli (air sacs in the lung). It is mainly caused because of Smoking. Shortness of breath is the most common symptom of emphysema. A cough, sometimes caused by the production of mucus, and wheezing may also be symptoms of emphysema. Stopping of smoking and bronchodilating medications along with steroid medications are the treatment of this disease. Hence, the correct answer is option C.

Smoking causes many lung diseases that can be nearly as bad as lung cancer. Tobacco contains many chemicals and particles like nicotine that  irritate the airways and the lungs.
Therefore, the correct answer is option B.

Prolonged smoking tends to stain the teeth and change its color, tooth decays and gum diseases.

Polycyclic aromatic hydrocarbons or PAHs are a group of powerful cancer-causing chemicals found in cigarettes that can damage DNA and set cells down the road to becoming tumours. PAHs tend to damage particular sections of DNA. We know that PAHs contribute to lung cancer in smokers because DNA damage can be seen at these sections in patients.  One PAH compound, benzopyrene, is notable for being the first chemical carcinogen to be discovered (and is one of many carcinogens found in cigarette smoke). Its consequences are so bad, even if the woman exposed to PAH pollution during pregnancy, then there is adverse birth outcomes including low birth weight, premature delivery and heart malformations, lower IQ and asthma. Cord blood of exposed babies shows DNA damage that has been linked to cancer.

• The leading causes of mouth cancer are tobacco and alcohol. The next major cause is cigarette smoking.
  
• Both are carcinogenic, which means they contain chemicals that can damage the DNA in cells and lead to cancer
  

Cigarette smoking causes lung cancer by damaging the cells that line the lungs. When we inhale cigarette smoke, which is full of cancer-causing substances (carcinogens), changes in the lung tissue begin almost immediately. At first our body may be able to repair this damage. But with each repeated exposure, normal cells that line our lungs are increasingly damaged. Over time, the damage causes cells to act abnormally and eventually cancer may develop. People who smoke cigarettes are 15 to 30 times more likely to get lung cancer or die from lung cancer than people who do not smoke. Even smoking a few cigarettes a day or smoking occasionally increases the risk of lung cancer. The more years a person smokes and the more cigarettes smoked each day, the more risk goes up. Cigarette smoking causes many types of cancer, including cancers of the lung, oesophagus, larynx (voice box), mouth, throat, kidney, bladder, pancreas, stomach, and cervix, as well as acute myeloid leukemia.

Emphysema is a progressive, incurable chronic lung infection. The air sacs or the alveoli are destroyed and oxygen uptake is restricted due to the loss of elasticity of lung tissue.
Thus, the correct answer is option (C), 'Emphysema'.

Nicotine is found in the leaves of tobacco. It acts as both stimulant as it mimics the acetylcholine and also as the depressor. It stimulates passage of nerve impulses causes muscles to relax. 

Smoking is a practice in which a substance is burned and the resulting smoke breathed in to be tasted and absorbed into the bloodstream.
Emphysema is a form of chronic lung disease, usually caused by smoking.
Bronchitis is caused by tobacco smoke, dust, fumes, vapors and air pollution.
Changes in lung tissue begin when one inhale cigarette smoke.
Therefore, the correct answer is option D.

A substance that causes cancer is called a carcinogen. Cigarette smoke contains more than 4,000 chemicals out of which 43 are carcinogenic. Some of the carcinogens are nicotine, formaldehyde, benzene, carbon monoxide, etc. Most of the cigarette smoke remains in the lungs. This smoke damages the lung walls causing cancer. Thus the correct answer is option B.

Nicotine is a major constituent of tobacco, which plays a critical role in smoking addiction. In humans, nicotine is primarily metabolized to cotinine, which is further metabolized to trans-3'-hydorxycotinine.
Thus, the correct answer is option (C), 'Cotinine'.

Addiction is a phenomenon in which there is physical or psychological need to do, take or use something. The various addictions are smoking, chewing pan, chewing gutkha, alcohol, etc. Out of these addictions, the most harmful addiction for the respiratory system is smoking. It causes respiratory diseases like bronchitis, emphysema, laryngitis, breathlessnes, lung irritation. Its continuous use also causes permanent damage to the alveoli of the lungs. Nicotine is the addictive drug which is used in cigarettes.