Final answer:
The factor that makes a summer job at a coal mine illegal for a 16-year old is exposure to hazardous substances. Coal mining operations involve exposure to dangerous substances such as coal dust, which can lead to respiratory problems. Lack of proper safety training and the risk of accidents also make it unsafe for young workers. Option A is correct.
Step-by-step explanation:
The factor that makes a summer job at a coal mine illegal for a 16-year old is exposure to hazardous substances (option A).
Coal mining operations often involve exposure to dangerous substances such as coal dust, which can lead to respiratory problems like black lung disease over time. Additionally, there is a risk of accidents, explosions, and cave-ins in coal mines, making it unsafe for young workers who may lack proper safety training and experience (option B).
While extended working hours (option C) and parental consent (option D) may be factors in certain job situations, the main concern with a coal mine job for a 16-year old is the potential for exposure to hazardous substances and lack of proper safety training.