by lowering temperatures and improving air quality. Hot weather worsens air pollution by turning car exhaust into smog, which can make life miserable for people with asthma（哮喘）and other breathing problems.

　　Of course, LA will have to do more than paint over a few streets to cool off the city. Angelinos will also need to plant more trees and apply white paint to rooftops--at least those not already covered in solar panels. While LA is a pioneer of reflective streets, other cities, like New York, are already experimenting with reflective roofs or, like Melbourne, lowering the temperature by planting trees. LA is hardly alone in its effort to stay cool.

　　"This is an urgent challenge, and it's much bigger than one person," said Mayor Garcetti in a recent statement. "Climate change is a fact of life that people in Los Angeles and cities around the world live with every day."

28. Which of the following contributes to the urban heat island effect?

　　A. Planting more trees in the streets.

　　B. Covering the streets with white paint.

　　C. Applying reflective paint to rooftops.

　　D. Furnishing every house with air conditioners.

29. What should the city officials emphasize during hot summer?

　　A. How to make the city cooler.

　　B. Where to wear a white shirt.

　　C. Why to coat the roads with black paint.

　　D. When to cut off the electricity supply.

30. What benefit can people gain from the use of CoolSeal?

　　A. Increasing the indoor activities.

　　B. Making life easier and more comfortable.

　　C. Reducing the number of cold days.

　　D. Promoting the sale of air conditioners.

31. What's the main idea of the passage?

　　A. L.A. is painting its streets white to keep the city cool.

　　B. L.A. calls on people to fight against global warming.

　　C. L.A. is alone suffering extreme heat.

　　D. More and more countries begin to plant trees in the streets.

D

　　Famous Chinese agricultural scientist Yuan Longping and his research team's experiment of planting saltwater-tolerant(耐盐的) rice in desert areas of Dubai in the United Arab Emirates(阿拉伯联合酋长国) proved to be a success, with one type of rice producing more than 7.5 tons per hectare(公顷), Xinhua reported.

　　Saltwater-tolerant rice is designed to grow in tidal flats (潮滩地) or other areas with heavy salt content. It was the world's first successful case of planting rice in a tropical(热带的) desert area, standing as China's contribution to improving the ability of people in desert areas to be self-sufficient(自给自足的) in main foods, a move that can protect global food security and improve the desert ecological environment.

In January, the center chose dozens of types of hybrid rice and planted them on small places of desert areas near Dubai. After five months of growth, the center invited experts from India,