A、Too little exercise. B、Heavy Internet use. C、Undue school pressure. D、Smoking and drinking. B

(5)A new study finds that heavy Internet use may be connected to high blood pressure in an unlikely group—teenagers.
   The study results show that teens who spend at least 14 hours a week online were more likely to have high blood pressure. (6)High blood pressure makes your heart and blood vessels work too hard. Over time, this extra strain increases your risk of a heart attack or stroke. High blood pressure can also cause heart and kidney disease. It is also closely linked to some forms of dementia, a brain disease. Dementia is marked by memory disorders, personality changes, and a reduced ability to reason. (7) The Henry Ford Hospital in Detroit, Michigan did the study. It involved 335 young people, from 14 to 17 years old. 134 of the teens were described as "heavy Internet users." (7)Researchers found that out of these 134 teens, 26 had high blood pressure. The researchers say the study is the first to connect heavy web use and high blood pressure.
5. What is harmful to teenagers according to the study?
6. What other diseases may be linked to high blood pressure?
7. What did the researchers find in the study?