Cities are taking interest in electric scooter-share systems as an affordable transportation to cut down on pollution and traffic jams. The electric scooters, which weigh between 30 and 40 pounds, reach speeds of about 15 mph.

    In September 2017，Santa Monica, California, became the first U.S. city to have an electric scooter-share service. Users find and unlock one of the more than 1，000 scooters with a smartphone app. A ride costs $ 1，and then 0.15 cents for each minute of riding throughout the beach town.

    Bird, the startup operating the scooter-share, picks up the scooters every night to them, and places them around Santa Monica each morning ready for people's use. The company was created by Travis VanderZanden, who once worked in Uber and Lyft, after he realized ridesharing services failed to help with traffic jams and air pollution. Since its September 2017 beginning, Bird's system has served more than 50,000 riders who have taken 250,000 trips — more than half of which have been in the last month. It's since expanded (扩 张) to Venice, California, and some neighborhoods in Los Angeles and San Diego. Bird plans to expand to lots of markets by the end of 2018.

    Competitors， backed by millionaires， are appearing. Two bike-share startups LimeBike and Spin, have spoken of plans to provide electric scooters in cities this year.

    Electric scooters have also gotten the attention of Mayor Pete Buttigieg from South Bend，Indiana. The city is interested in using them as a way to improve public transportation. South Bend was one of the first to use bike-share systems, which allow people to park ridesharing bikes on public land. “We love to be early pioneers，” said Buttigieg. “If we work out the safety problem, we would be open to welcoming the technology.”

    “We need to make sure these new transportation systems are lawful and safe for users，”Constance Farrell，a spokeswoman for the city of Santa Monica told CNN. “We would like to see electric scooters continue to operate in the city. They are in line with our goal of multi-modal living and carbon-light living. ” According to Farrell，there have been eight accidents, including one with a serious head injury， in Santa Monica after the scooters rolled out. Users are required to have a driver's license (驾 照），shouldn't ride on sidewalks or have other passengers on board.

    Bird has given out free helmets to some riders and tells its users to ride in bike lanes, but some users ride on sidewalks, and most U.S. streets don't have bike lanes.

    “The global community of cities is going to have to work this all out for scooters，”Buttigieg said. “They can move unbelievably quickly. That's exciting，and a little dangerous. ”

    Layla and her family were driving to the town park. It was a hot day. She wanted to swim in the lake. As they got out of the car, Layla saw ____ (she) friends.

    "Let's go into the water!" she called. All the kids jumped in ____ (happy).

    Layla always has fun at the park. In spring, Layla's dad often takes her fishing in ____(冠词) lake. They usually go early in the morning. The lake water is still (平静的). It is different ____ (介词) the river, which has water that runs by

    In summer, ____ (family) have picnics near the lake. The kids play and swim in the lake.

    In the morning of autumn, the lake has fog (雾) over it. Layla's dad once____ (tell) her something about fog: Hot summer days warm the water, and then cool autumn air ____ (move) over the lake's warm water. The water vapor(水蒸汽) in the air gets cool. It ____ (become) small drops of water (水珠). We can see those drops of water hang in the air as fog.

    Layla loves winter at the park too. The cold ____ (temperature) turn the water into ice. Many people go skating on the ice.

    The lake looks different at different times of the year, ____ (连词) it is always a good place to have fun!