Pick one type of unhealthy risk-taking behavior, and describe how that behavior might contribute to specific injuries

Very random: smoking. 
You know actually smoking is very bad for you, even though people like it a lot, and get sticked with it their whole life. Chemicals in cigarettes have been shown to affect the brain in a way that’s similar to how drugs like heroin cause addiction.  Smoking also affects your lungs. They get black, because of the smoke, and all the chemicals that they have. Cigarette smoke is filled with harmful chemicals including nicotine, hydrogen cyanide and carbon monoxide. So gathering this all up: u can get lung cancer if you smoke. 
Hope i helped a lot!