13.
In the past, city parks were welcoming escapes from noise. People looked forward to spending quiet time under sunny skies and park trees. But, things have changed for the worse recently. According to environmentalists, many city parks are now too noisy for quiet reading, walks, or picnics. About 10 percent of the world's parks are now affected by exceedingly high noise pollution. Most of this noise is due to loud music, car horns, and airplanes flying overhead. MAIN IDEA: Quiet city parks have changed for the worse. Which of the following reasons supports the main idea by explaining how?