Please Answer Correct One.

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"A study is conducted to assess the risk for developing asthma among children exposed to industrial pollution. A total of 20,000 children ages 6 months to 11 years who live in an industrial area are observed for 10 years. The control group consists of 10,000 children who live in a rural area that is 100 km (62 miles) from the nearest industrial site. Each subject undergoes yearly examination and asthma testing for the duration of the study, and all changes in respiratory function are noted. Results show that the incidence of asthma is 2.4 times higher in children living in an industrial area compared with the control group (p