Which of the following diseases is linked to smoking?

Lung cancer is strongly linked to smoking due to the harmful chemicals present in tobacco smoke. When a person smokes, they inhale a mixture of over 7,000 chemicals, many of which are known carcinogens, meaning they can cause cancer. These carcinogens damage the cells in the lungs over time, leading to mutations and the uncontrolled growth of cells—this process contributes to the development of lung cancer.

While other conditions such as asthma and respiratory infections like tuberculosis can be exacerbated by smoking, they are not primarily caused by it in the same direct manner as lung cancer. Diabetes, while complex and influenced by various factors including lifestyle and genetics, does not have a direct cause-and-effect relationship with smoking like lung cancer does. Therefore, lung cancer remains the most clear-cut disease directly linked to the act of smoking itself.