If you had no knowledge of the subject then According to the American Academy of Pediatrics (AAP), children and infants are among the most susceptible to many air pollutants- this claim should be the most credible.
Option: 2
Step-by-step explanation:
If a person do not have any knowledge about environment related matter but have to believe some stement only by some common sense then the given context that according to the American Academy of Pediatrics children and infants are among the most susceptible to many air pollution.
It is because children and infants have much less immunity power in comparison with adults. They are more prone to attack by diseases. Polluted air consists of harmful gases which affect child's health. As it is a report of doctor's organization that's why its reliable more.