Final answer:
The statement regarding Nicotiana tobacum being the major commercial species of tobacco is true. Tobacco smoke contains many harmful chemicals, including nicotine, tar, and carbon monoxide. The comparison between the addictiveness of nicotine and heroin is complex but both are significantly harmful.
Step-by-step explanation:
The statement that the major commercial species of tobacco is Nicotiana tobacum is true. Tobacco smoke contains numerous toxic chemicals that pose health risks. Three particularly harmful toxins present in tobacco smoke are nicotine, which is highly addictive and can raise blood pressure and heart rate; tar, which contains multiple cancer-causing particles and can damage the lungs by clogging bronchial tubes; and carbon monoxide, which binds to hemoglobin in red blood cells, reducing the ability of the blood to carry oxygen throughout the body.
Regarding the addictiveness of nicotine, it is a highly debated topic. While some studies suggest nicotine is as addictive as drugs like heroin, it is a complex comparison that involves different aspects of dependency and withdrawal. It is critical to understand that both substances are highly addictive and harmful to health.