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19 tháng 4 2017
In 1966, engineer Ralph Baer invented the "Brown Box" prototype that enabled companies to create home video-gaming systems. The introduction of home computers has taken video gaming to a new dimension. Children now have a huge array of choices regarding when and how they play their computer games. Playing some types of computer games may have some minor advantages for children, according to studies reported by Palo Alto Medical Foundation. Too much time spent playing computer games, however, also has the potential for negative impacts on emotional, physical and social development such as violent content, health risks,...
Violent Content
Teens who spend too much time playing computer games -- particularly those games with violent content -- risk having problems with violent and aggressive behavior, according to studies reported by the Palo Alto Medical Foundation. Teenagers learn to identify with game characters, and repeated use of games that promote violence and aggression make it difficult for some adolescents to separate real life from the imaginary "first-person" gaming experience. The American Academy of Pediatrics recommends that parents guide children to select high-quality games appropriate for the age of the child, and also advises that parents restrict the child's daily exposure to all media to a maximum of two hours.
Health Risks
While studies reported by the Health Physics Society show that there are no proven radiation-related health risks linked to computers and monitors, the level of screen brightness and the length of time that children spend focusing on the computer monitor sometimes leads to eye strain. Optometrist Gary Heiting warns parents that prolonged gaming play in front of a monitor can also lead to computer vision syndrome, a condition that may cause progressive nearsightedness. Sitting in front of a computer for prolonged periods may create ergonomic problems from poor body positioning, or from the position of the computer and screen. Children also risk developing carpal tunnel syndrome in wrists from repetitive play.
1 tháng 6 2017
Đáp án B
Đặc điểm chung của các phân tử hợp chất hữu cơ là
1. thành phần nguyên tố chủ yếu là C và H.
2. có thể chứa nguyên tố khác như Cl, N, P, O.
3. liên kết hóa học chủ yếu là liên kết cộng hoá trị.
8 tháng 9 2017
Đáp án D
(1) Thành phần nguyên tố chủ yếu là C và H.
(2) Có thể chứa nguyên tố khác như Cl, N, P, O.
(3) Liên kết hóa học chủ yếu là liên kết cộng hoá trị
- Cho hỏi nha : min à
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