Read the excerpt . which phrase is a context clue that can determine the meaning of the word "demographic"

plenty of evidence exists about the hazards involved with smoking, leading experts to believe that quitting smoking at any point will result in improved health. but due to the addictive nature of smoking cigarettes, many people will find quitting to be difficult, if not totally impossible. still, if a person cannot quit, he or she should consider the impact of smoking may have on those around them, particularly young children and infants. the lungs, nervous system, and immune system of young children are still developing. this development places children as a demographic group at an even greater risk of being harmed by secondhand smoke than people in older age groups. young children are more likely to develop lung problems, allergies, and other medical conditions when they are frequently in the presence of a smoker. some evidence has even linked sudden infant death syndrome (sids) to secondhand smoking.

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