根据问题填空：

    Beijing was once a city of bikes, known as the Bicycle Kingdom____ cars were reserved for official business and the politically powerful. However, decades of economic____ (grow) led to a huge flowing of cars in the city. Owning one became not just a marker of reaching the middle class but also a requirement for marriage. As the economy developed, autos pushed bikes off the roads____ (create) heavy pollution and miserable traffic.

    ____(fortunate), now Beijing may he returning to its roots. Thanks to about 20 technology companies, brightly colored shared bikes ____(flood) into Beijing in the last two years. Many local residents welcome the shared bikes____the flexibility and freedom they offer. They pick up the bikes and then ride and drop____ off anywhere they like, locking the back wheel, with no need to find a fixed place.

    Analyses in China say it is three factors that contribute to bikes ____(increase) rapidly: a lot of cash looking for a home, a good idea and government support. “As the city s population grew, traffic jams got ____ (bad).” Cai, the Ofo spokeswoman, said, “Shared bikes could solve the 'last mile' problem in ____ environmentally friendly way.”

— I'm waiting for my friend. If he_______, I________ swimming alone.